[1] Flywheel is an important part of a steam engine because it -
A.
gives strength to the engine
B.
accelerates the speed of the engine
C.
helps the engine in keeping the speed uniform
D.
decreases the moment of Inertia
Ans:
helps the engine in keeping the speed uniform
Explanation :
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed, enabling the engine to run at a constant, uniform motion. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.
[2] The bats can fly in the dark because –
A.
They can see the objects in darkness
B.
They have weak legs and are likely to be attacked by predators
C.
They generate flashes of light
D.
They generate ultrasonic sound waves
Ans:
They generate flashes of light
Explanation :
Bats use echolocation to navigate and forage, often in total darkness. They generally emerge from their roosts in caves, attics, or trees at dusk and hunt for insects into the night. Their use of echolocation allows them to occupy a niche where there are often many insects (that come out at night since there are fewer predators then) and where there is less competition for food, and where there are fewer other species that may prey on the bats themselves. Microbats generate ultrasound via the larynx and emit the sound through the open mouth or, much more rarely, the nose.
[3] A microscope used in pathological laboratories forms –
A.
magnified, virtual, erect, Image
B.
diminished, real and erect image
C.
Magnified, virtual and inverted image
D.
Diminished, virtual and erect image
Ans:
Magnified, virtual and inverted image
Explanation :
A microscope is an instrument that produces a clear magnified image of an object viewed through it. A basic microscope is made up of two converging lenses. The first lens creates a real image which serves as the object for the second lens, and the image created by the second lens is the one a viewer sees. The final image is virtual and is inverted compared to the original object.
[4] It is dangerous to observe solar eclipse with naked eyes because –
A.
Infrared radiations from sun burn our retina
B.
Ultraviolet radiations from Sun burn our retina
C.
All radiations from sun initiate chemical reactions in eyes
D.
Cosmic rays reach eyes more during the eclipse
Ans:
Ultraviolet radiations from Sun burn our retina
Explanation :
The solar radiation that reaches the surface of Earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the meter range. The tissues in the eye transmit a substantial part of the radiation between 380 and 1400 nm to the light-sensitive retina at the back of the eye. The concern over improper viewing of the Sun during an eclipse is for the development of "eclipse blindness" or retinal burns.
[5] The wall of a dam is broader at the base –
A.
because streamlining is required
B.
to withstand pressure that increases with depth
C.
to withstand pressure that increases in a horizontal plane
D.
to withstand pressure that is increased with atmospheric pressure
Ans:
to withstand pressure that increases with depth
Explanation :
Darns are built broader at the base for two reasons. The first is because it needs to be stable enough to support the dam, and two, the bottom of the dam needs to be able to deal with the increased pressure of the water, as you get further down. Particular to dams, at the lower part of the structure the lower levels of water are at higher pressure than the upper levels of the water.
[6] A transformer –
A.
converts DC to AC
B.
is used to decrease or increase AC voltage
C.
converts AC voltage to D.C. voltage
D.
converts electrical energy into mechanical energy
Ans:
is used to decrease or increase AC voltage
Explanation :
Transformers have made long-distance transmission of electric power a practical reality, as AC voltage can be "stepped up" and current "stepped down" for reduced wire resistance power losses along power lines connecting generating stations with loads. At either end (both the generator and at the loads), voltage levels are reduced by transformers for safer operation and less expensive equipment.
[7] 'Mirage' is an example of –
A.
refraction of light only
B.
total internal, reflection of light only
C.
refraction and total internal reflection of light
D.
dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. In contrast to a hallucination, a mirage is a real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient.
[8] The absolute zero is a temperature at which _.
A.
molecular motion in a gas would cease
B.
water freezes
C.
all gases become liquid
D.
all gases become solid
Ans:
molecular motion in a gas would cease
Explanation :
Absolute zero is the lowest possible temperature where nothing could be colder and no heat energy remains in a substance. It is the point at which all motion in matter stops. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and –273.15 degrees Celsius on the Celsius scale.
[9] Surface tension in a liquid is due to :
A.
Adhesive force between molecules
B.
Cohesive force between molecules
C.
Gravitational force between molecules
D.
Electrical force between molecules
Ans:
Cohesive force between molecules
Explanation :
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
[10] When a vehicle passes, TV reception gets distorted. This is because –
A.
metal reflects radiowaves
B.
spark plug creates electromagnetic disturbances
C.
vehicle pollution affects the performance of the TV components
D.
modern vehicles use electro ignition system
Ans:
spark plug creates electromagnetic disturbances
Explanation :
This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.
[11] The snow on the mountains does NOT melt all at once when it is heated by the sum because:
A.
It becomes very hard
B.
It reflects most of the heat from the sum
C.
it has a low specific heat capacity
D.
it has a high latent heat of fusion
Ans:
It reflects most of the heat from the sum
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
A flywheel is a rotating mechanical device that is used to store rotational energy. Flywheels have a significant moment of inertia and thus resist changes in rotational speed, enabling the engine to run at a constant, uniform motion. In the Industrial Revolution, James Watt contributed to the development of the flywheel in the steam engine.
[2] The bats can fly in the dark because –
A.
They can see the objects in darkness
B.
They have weak legs and are likely to be attacked by predators
C.
They generate flashes of light
D.
They generate ultrasonic sound waves
Ans:
They generate flashes of light
Explanation :
Bats use echolocation to navigate and forage, often in total darkness. They generally emerge from their roosts in caves, attics, or trees at dusk and hunt for insects into the night. Their use of echolocation allows them to occupy a niche where there are often many insects (that come out at night since there are fewer predators then) and where there is less competition for food, and where there are fewer other species that may prey on the bats themselves. Microbats generate ultrasound via the larynx and emit the sound through the open mouth or, much more rarely, the nose.
[3] A microscope used in pathological laboratories forms –
A.
magnified, virtual, erect, Image
B.
diminished, real and erect image
C.
Magnified, virtual and inverted image
D.
Diminished, virtual and erect image
Ans:
Magnified, virtual and inverted image
Explanation :
A microscope is an instrument that produces a clear magnified image of an object viewed through it. A basic microscope is made up of two converging lenses. The first lens creates a real image which serves as the object for the second lens, and the image created by the second lens is the one a viewer sees. The final image is virtual and is inverted compared to the original object.
[4] It is dangerous to observe solar eclipse with naked eyes because –
A.
Infrared radiations from sun burn our retina
B.
Ultraviolet radiations from Sun burn our retina
C.
All radiations from sun initiate chemical reactions in eyes
D.
Cosmic rays reach eyes more during the eclipse
Ans:
Ultraviolet radiations from Sun burn our retina
Explanation :
The solar radiation that reaches the surface of Earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the meter range. The tissues in the eye transmit a substantial part of the radiation between 380 and 1400 nm to the light-sensitive retina at the back of the eye. The concern over improper viewing of the Sun during an eclipse is for the development of "eclipse blindness" or retinal burns.
[5] The wall of a dam is broader at the base –
A.
because streamlining is required
B.
to withstand pressure that increases with depth
C.
to withstand pressure that increases in a horizontal plane
D.
to withstand pressure that is increased with atmospheric pressure
Ans:
to withstand pressure that increases with depth
Explanation :
Darns are built broader at the base for two reasons. The first is because it needs to be stable enough to support the dam, and two, the bottom of the dam needs to be able to deal with the increased pressure of the water, as you get further down. Particular to dams, at the lower part of the structure the lower levels of water are at higher pressure than the upper levels of the water.
[6] A transformer –
A.
converts DC to AC
B.
is used to decrease or increase AC voltage
C.
converts AC voltage to D.C. voltage
D.
converts electrical energy into mechanical energy
Ans:
is used to decrease or increase AC voltage
Explanation :
Transformers have made long-distance transmission of electric power a practical reality, as AC voltage can be "stepped up" and current "stepped down" for reduced wire resistance power losses along power lines connecting generating stations with loads. At either end (both the generator and at the loads), voltage levels are reduced by transformers for safer operation and less expensive equipment.
[7] 'Mirage' is an example of –
A.
refraction of light only
B.
total internal, reflection of light only
C.
refraction and total internal reflection of light
D.
dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. In contrast to a hallucination, a mirage is a real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient.
[8] The absolute zero is a temperature at which _.
A.
molecular motion in a gas would cease
B.
water freezes
C.
all gases become liquid
D.
all gases become solid
Ans:
molecular motion in a gas would cease
Explanation :
Absolute zero is the lowest possible temperature where nothing could be colder and no heat energy remains in a substance. It is the point at which all motion in matter stops. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and –273.15 degrees Celsius on the Celsius scale.
[9] Surface tension in a liquid is due to :
A.
Adhesive force between molecules
B.
Cohesive force between molecules
C.
Gravitational force between molecules
D.
Electrical force between molecules
Ans:
Cohesive force between molecules
Explanation :
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
[10] When a vehicle passes, TV reception gets distorted. This is because –
A.
metal reflects radiowaves
B.
spark plug creates electromagnetic disturbances
C.
vehicle pollution affects the performance of the TV components
D.
modern vehicles use electro ignition system
Ans:
spark plug creates electromagnetic disturbances
Explanation :
This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.
[11] The snow on the mountains does NOT melt all at once when it is heated by the sum because:
A.
It becomes very hard
B.
It reflects most of the heat from the sum
C.
it has a low specific heat capacity
D.
it has a high latent heat of fusion
Ans:
It reflects most of the heat from the sum
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
A microscope is an instrument that produces a clear magnified image of an object viewed through it. A basic microscope is made up of two converging lenses. The first lens creates a real image which serves as the object for the second lens, and the image created by the second lens is the one a viewer sees. The final image is virtual and is inverted compared to the original object.
[4] It is dangerous to observe solar eclipse with naked eyes because –
A.
Infrared radiations from sun burn our retina
B.
Ultraviolet radiations from Sun burn our retina
C.
All radiations from sun initiate chemical reactions in eyes
D.
Cosmic rays reach eyes more during the eclipse
Ans:
Ultraviolet radiations from Sun burn our retina
Explanation :
The solar radiation that reaches the surface of Earth ranges from ultraviolet (UV) radiation at wavelengths longer than 290 nm to radio waves in the meter range. The tissues in the eye transmit a substantial part of the radiation between 380 and 1400 nm to the light-sensitive retina at the back of the eye. The concern over improper viewing of the Sun during an eclipse is for the development of "eclipse blindness" or retinal burns.
[5] The wall of a dam is broader at the base –
A.
because streamlining is required
B.
to withstand pressure that increases with depth
C.
to withstand pressure that increases in a horizontal plane
D.
to withstand pressure that is increased with atmospheric pressure
Ans:
to withstand pressure that increases with depth
Explanation :
Darns are built broader at the base for two reasons. The first is because it needs to be stable enough to support the dam, and two, the bottom of the dam needs to be able to deal with the increased pressure of the water, as you get further down. Particular to dams, at the lower part of the structure the lower levels of water are at higher pressure than the upper levels of the water.
[6] A transformer –
A.
converts DC to AC
B.
is used to decrease or increase AC voltage
C.
converts AC voltage to D.C. voltage
D.
converts electrical energy into mechanical energy
Ans:
is used to decrease or increase AC voltage
Explanation :
Transformers have made long-distance transmission of electric power a practical reality, as AC voltage can be "stepped up" and current "stepped down" for reduced wire resistance power losses along power lines connecting generating stations with loads. At either end (both the generator and at the loads), voltage levels are reduced by transformers for safer operation and less expensive equipment.
[7] 'Mirage' is an example of –
A.
refraction of light only
B.
total internal, reflection of light only
C.
refraction and total internal reflection of light
D.
dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. In contrast to a hallucination, a mirage is a real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient.
[8] The absolute zero is a temperature at which _.
A.
molecular motion in a gas would cease
B.
water freezes
C.
all gases become liquid
D.
all gases become solid
Ans:
molecular motion in a gas would cease
Explanation :
Absolute zero is the lowest possible temperature where nothing could be colder and no heat energy remains in a substance. It is the point at which all motion in matter stops. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and –273.15 degrees Celsius on the Celsius scale.
[9] Surface tension in a liquid is due to :
A.
Adhesive force between molecules
B.
Cohesive force between molecules
C.
Gravitational force between molecules
D.
Electrical force between molecules
Ans:
Cohesive force between molecules
Explanation :
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
[10] When a vehicle passes, TV reception gets distorted. This is because –
A.
metal reflects radiowaves
B.
spark plug creates electromagnetic disturbances
C.
vehicle pollution affects the performance of the TV components
D.
modern vehicles use electro ignition system
Ans:
spark plug creates electromagnetic disturbances
Explanation :
This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.
[11] The snow on the mountains does NOT melt all at once when it is heated by the sum because:
A.
It becomes very hard
B.
It reflects most of the heat from the sum
C.
it has a low specific heat capacity
D.
it has a high latent heat of fusion
Ans:
It reflects most of the heat from the sum
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
Darns are built broader at the base for two reasons. The first is because it needs to be stable enough to support the dam, and two, the bottom of the dam needs to be able to deal with the increased pressure of the water, as you get further down. Particular to dams, at the lower part of the structure the lower levels of water are at higher pressure than the upper levels of the water.
[6] A transformer –
A.
converts DC to AC
B.
is used to decrease or increase AC voltage
C.
converts AC voltage to D.C. voltage
D.
converts electrical energy into mechanical energy
Ans:
is used to decrease or increase AC voltage
Explanation :
Transformers have made long-distance transmission of electric power a practical reality, as AC voltage can be "stepped up" and current "stepped down" for reduced wire resistance power losses along power lines connecting generating stations with loads. At either end (both the generator and at the loads), voltage levels are reduced by transformers for safer operation and less expensive equipment.
[7] 'Mirage' is an example of –
A.
refraction of light only
B.
total internal, reflection of light only
C.
refraction and total internal reflection of light
D.
dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. In contrast to a hallucination, a mirage is a real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient.
[8] The absolute zero is a temperature at which _.
A.
molecular motion in a gas would cease
B.
water freezes
C.
all gases become liquid
D.
all gases become solid
Ans:
molecular motion in a gas would cease
Explanation :
Absolute zero is the lowest possible temperature where nothing could be colder and no heat energy remains in a substance. It is the point at which all motion in matter stops. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and –273.15 degrees Celsius on the Celsius scale.
[9] Surface tension in a liquid is due to :
A.
Adhesive force between molecules
B.
Cohesive force between molecules
C.
Gravitational force between molecules
D.
Electrical force between molecules
Ans:
Cohesive force between molecules
Explanation :
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
[10] When a vehicle passes, TV reception gets distorted. This is because –
A.
metal reflects radiowaves
B.
spark plug creates electromagnetic disturbances
C.
vehicle pollution affects the performance of the TV components
D.
modern vehicles use electro ignition system
Ans:
spark plug creates electromagnetic disturbances
Explanation :
This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.
[11] The snow on the mountains does NOT melt all at once when it is heated by the sum because:
A.
It becomes very hard
B.
It reflects most of the heat from the sum
C.
it has a low specific heat capacity
D.
it has a high latent heat of fusion
Ans:
It reflects most of the heat from the sum
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
A mirage is a naturally occurring optical phenomenon in which light rays are bent to produce a displaced image of distant objects or the sky. In contrast to a hallucination, a mirage is a real optical phenomenon which can be captured on camera, since light rays actually are refracted to form the false image at the observer's location. As light passes from colder air across a sharp boundary to significantly warmer air, the light rays bend away from the direction of the temperature gradient.
[8] The absolute zero is a temperature at which _.
A.
molecular motion in a gas would cease
B.
water freezes
C.
all gases become liquid
D.
all gases become solid
Ans:
molecular motion in a gas would cease
Explanation :
Absolute zero is the lowest possible temperature where nothing could be colder and no heat energy remains in a substance. It is the point at which all motion in matter stops. By international agreement, absolute zero is defined as precisely; 0 K on the Kelvin scale, which is a thermodynamic (absolute) temperature scale; and –273.15 degrees Celsius on the Celsius scale.
[9] Surface tension in a liquid is due to :
A.
Adhesive force between molecules
B.
Cohesive force between molecules
C.
Gravitational force between molecules
D.
Electrical force between molecules
Ans:
Cohesive force between molecules
Explanation :
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
[10] When a vehicle passes, TV reception gets distorted. This is because –
A.
metal reflects radiowaves
B.
spark plug creates electromagnetic disturbances
C.
vehicle pollution affects the performance of the TV components
D.
modern vehicles use electro ignition system
Ans:
spark plug creates electromagnetic disturbances
Explanation :
This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.
[11] The snow on the mountains does NOT melt all at once when it is heated by the sum because:
A.
It becomes very hard
B.
It reflects most of the heat from the sum
C.
it has a low specific heat capacity
D.
it has a high latent heat of fusion
Ans:
It reflects most of the heat from the sum
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
Surface tension is a contractive tendency of the surface of a liquid that allows it to resist an external force. This property is caused by cohesion of similar molecules, and is responsible for many of the behaviors of liquids.
[10] When a vehicle passes, TV reception gets distorted. This is because –
A.
metal reflects radiowaves
B.
spark plug creates electromagnetic disturbances
C.
vehicle pollution affects the performance of the TV components
D.
modern vehicles use electro ignition system
Ans:
spark plug creates electromagnetic disturbances
Explanation :
This is caused due to the interference caused by the electromagnetic waves generated by a passing vehicle. These waves were within the same frequency range as that of the waves of TV reception and hence caused Interference. Interference is a phenomenon in which two waves superimpose to form a resultant wave of greater or lower amplitude. Interference usually refers to the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, and surface water waves and due to the interference caused by the vehicle electromagnetic disturbances occurs in the TV reception and gets distorted.
[11] The snow on the mountains does NOT melt all at once when it is heated by the sum because:
A.
It becomes very hard
B.
It reflects most of the heat from the sum
C.
it has a low specific heat capacity
D.
it has a high latent heat of fusion
Ans:
It reflects most of the heat from the sum
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
Newly formed snow reflects about 90 per cent of the sunlight that falls upon it. This means that the sun is powerless to melt clean snow. And when snow does melt, it is not because of the sunlight. Snow does not melt on a spring day because of the sun's heat. It melts because of the warm air from the sea.
[12] The water from a hand pump is warm in winter because -
A.
our body is cold in winter and the water appears to be warm
B.
the temperature inside the Earth is higher than the atmospheric temperature
C.
the pumping process causes friction which warms up the water
D.
inside water comes out and absorbs heat from the environment
Ans:
the temperature inside the Earth is higher than the atmospheric temperature
Explanation :
In winter, the outside temperature is lower than that of water flowing out of the pump, and therefore, the water is warm. Whereas in summer, the outside temperature is higher than the water of the pump, and therefore, it feels cold.
[13] ‘Mirage' is an example of -
A.
Refraction of light only
B.
Total internal reflection of light only
C.
Refraction and total internal reflection of light
D.
Dispersion of light only
Ans:
refraction and total internal reflection of light
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
Mirages are examples of total internal reflection. The conditions most likely to produce a mirage in the desert would be a layer of hot air lying immediately above the ground with cooler air above it (this is quite usual during the day because the ground becomes so hot).
[14] It is easier to carry two buckets of water in one hand each, than to carry only one in one hand because –
A.
weights of buckets are balanced
B.
centre of gravity falls within the body
C.
centre of gravity and centre of equilibrium fall within the feet
D.
resultant weight of buckets is zero
Ans:
centre of gravity and centre of equilibrium fall within the feet
Explanation :
When the buckets containing equal amount of water are held in both hands, weight is spaced out more evenly than it would be if one had to carry a single bucket. For balancing the weight, the centre of gravity and the centre of equilibrium should fall, in the present case, within the feet.
[15] If a band is played on the moon the sound will -
A.
reverberate
B.
be heard by us faintly
C.
be heard upto 10km from it
D.
not be heard at any distance at all from it
Ans:
not be heard at any distance at all from it
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
As there is no atmosphere surrounding the moon, the sound from any band that is played there cannot travel outwards there is no material medium surrounding it for its propagation.
[16] Dynamo is a device for converting –
A.
Heat energy into electrical energy
B.
Mechanical energy into electrical energy
C.
Magnetic energy into electrical energy
D.
Chemical energy into electrical energy
Ans:
Mechanical energy into electrical energy
Explanation :
A dynamo is a device for converting mechanical energy into electrical energy, esp. one that produces direct current. A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[17] The magnifying power of an astronomical telescope can be decreased by –
A.
decreasing the focal length of the eyepiece
B.
increasing the focal length of the eyepiece
C.
increasing the focal length of the objective
D.
None of these
Ans:
increasing the focal length of the eyepiece
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
The magnifying power (M) of astronomical is given by M = (focal length of objective)/(focal length of eye piece). This expression shows that in order to obtain high magnification, focal length of object must be large and that of eye piece should be small. Similarly, for decreased magnification, focal length of eye piece should be increased.
[18] Which of the following events occurred first?
A.
Albert Einstein propounded the General Theory of Relativity
B.
Max Planck unveiled the Quantum Theory
C.
Marconi first transmitted a wireless signal
D.
Madame Marie Curie be-came the first woman Nobel Prize winner
Ans:
Max Planck unveiled the Quantum Theory
Explanation :
General Theory of Relativity: a theory of gravitation developed by Einstein in the years 1907-1915; Quantum Theory of Max Planck: 1900; Transmission of wireless signal by Marconi: first Atlantic wireless transmission on December 11, 1901; and Madame Curie becoming the first woman Nobel Prize winner: shared her 1903 Nobel Prize in Physics with her husband Pierre Curie.
[19] The velocity of sound in air –
A.
decreases with increase of temperature
B.
increases with decrease of temperature
C.
does not depend on temperature
D.
decreases with decrease of temperature
Ans:
decreases with decrease of temperature
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
Assuming air to be an ideal gas, the speed of sound c depends on temperature only, not on the pressure or density. As air temperature increases, so does the speed of sound and vice versa. This is due to the individual air particles having extra kinetic energy at higher temperatures and lesser at lower temperatures.
[20] The sensation of weightlessness in a spacecraft in an orbit is due to the –
A.
Absence of gravity outside
B.
Acceleration in the orbit which is equal to the acceleration due to gravity outside
C.
Presence of gravity outside but not inside the spacecraft
D.
Fact that spacecraft in the orbit has no energy
Ans:
Acceleration in the orbit which is equal to the acceleration due to gravity outside
Explanation :
Weightlessness in space is caused by the simple physical factors that cause the limitation of gravity. While on Earth, external forces are pushing or pulling on a person's body, however when a spacecraft enters orbit, the people and objects aboard the craft enter a state of free fall. Essentially, the vehicle and all of its contents are falling towards the Earth causing the sensation of weightlessness similar to the state a person feels when enjoying the amusement park ride. Many people believe that a lack of gravity is the root cause for weightlessness in space.
[21] Energy in reflected light :
A.
does not depends on the angle of incidence
B.
increases with the increase in angle
C.
decreases with the increase in angle of incidence
D.
becomes maximum for angle of incidence equal to 45°
Ans:
increases with the increase in angle
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
Reflected waves are simply those waves that are neither transmitted nor absorbed, but are reflected from the surface of the medium they encounter. The amount of incident-wave energy that is reflected from a surface depends on the nature of the surface and the angle at which the wave strikes the surface.
[22] A person standing on a railway platform listens to the whistles of arriving and departing trains. The whistle heard is –
A.
the same in both cases in all respects
B.
of higher intensity when train arrives
C.
of higher pitch when train arrives
D.
of higher pitch when train departs
Ans:
of higher pitch when train arrives
Explanation :
Sound is a sequence of waves of pressure that propagates through compressible media such as air or water. (Sound can propagate through solids as well, but there are additional modes of propagation).
[23] A dynamo is a device which –
A.
creates mechanical energy
B.
creates electrical energy
C.
converts mechanical energy into electrical energy
D.
converts electrical energy into mechanical energy
Ans:
converts mechanical energy into electrical energy
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
A dynamo is an electrical generator that produces direct current with the use of a commutator. Dynamos were the first electrical generators capable of delivering power for industry, and the foundation upon which many other later electric-power conversion devices were based, including the electric motor, the alternating-current alternator, and the rotary converter.
[24] A piece of paper and a cricket ball are dropped from the same height. Under which of the following conditions do both reach the surface simultaneously?
A.
They must have the same volume
B.
They must have the same density
C.
They must have the same mass
D.
They must be dropped in vacuum
Ans:
They must be dropped in vacuum
Explanation :
When a piece of paper and a cricket ball are dropped from the same height, they reach the surface at different time because the shape of the paper is more flat and it behaves like a parachute causing more air resistance acting on it with respect to the ball. But, in order to reach the surface at the same tim e by both the articles, they must be dropped in vacuum. It is because in vacuum there is no other force other than force of gravity occurring on them and this leads to a conclusion that both the article reaches at the same time.
[25] Woollen cloth protects the body from cold because –
A.
it is a good conductor of heat
B.
it is a poor conductor of heat
C.
external heat rays enter into the body through the woollen cloth
D.
it reflects heat
Ans:
it is a poor conductor of heat
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.
Explanation :
It is just because woolen clothes have fibres and between those fibres air is trapped which reduces heat loss. It reduces heat loss because it is an insulator or poor conductor of heat.