# Physics MCQs Set – 3

## Question 1.

Sound travels at the fastest speed in

A. steel
B. water
C. air
D. vacuum

above

## Question 2.

On a cold day when a room temperature is 15oC, the metallic cap of a pen becomes much colder than its plastic body, though both are at the same temperature of 15oC, because

A. metals have higher thermal capacity than plastics
B. plastics have a lower density than metals
C. metals are good conductor of heat
D. plastics have a higher thermal conductivity than metals

Ans: C. metals are good conductor of heat

## Question 3.

Light Emitting Diodes (LED) is used in fancy electronic devices such as toys emit

A. X-rays
B. ultraviolet light
C. visible light

Ans: C. visible light

## Question 4.

Supersonic plane fly with the speed

A. less than the speed of sound
B. of sound
C. greater than the speed of sound
D. of light

Ans: C. greater than the speed of sound

## Question 5.

Oil raise up the wick in a lamp. The principle involves

A. the diffusion of oil through the wick
B. the liquid state of oil
C. capillary action phenomenon
D. volatility of oil

Ans: C. capillary action phenomenon

## Question 6.

Sound produced at a point is heard by a person after 5 second, while the same sound is heard by another person after 6 seconds. If the speed of sound is 300 m/s, what could be the maximum and minimum distances between the two persons?

A. 1.8 km, 0.15 km
B. 2.2 km, 0.20 km
C. 2.8 km, 0.25 km
D. 3.3 km, 0.30 km

Ans: D. 3.3 km, 0.30 km

## Question 7.

Out of the following pairs, which one does not have identical dimension?

A. Moment of inertia and moment of a force
B. Work and Torque
C. Angular momentum and Planck’s constant
D. Impulse and Momentum

Ans: A. Moment of inertia and moment of a force

## Question 8.

Mach number is used in connection with the speed of

A. sound
B. aircraft
C. spacecraft
D. ships

Ans: B. aircraft

## Question 9.

Superconductors are substances which

A. conduct electricity at low temperature
B. offer high resistance to the flow of current
C. offer no resistance to the flow of electricity
D. conduct electricity at high temperatures

Ans: C. offer no resistance to the flow of electricity

## Question 10.

Intensity of sound at a point is __ its distance from the source.

A. directly proportional to
B. inversely proportional to
C. directly proportional to square of
D. inversely proportional to square of

Ans: D. inversely proportional to square of

## Question 11.

Mercury is commonly used as a thermometric fluid rather than water because

A. specific heat of mercury is less than water
B. specific heat of mercury is more than water
C. mercury has greater visibility than water
D. density of mercury is more than the water

Ans: C. mercury has greater visibility than water

## Question 12.

On a stationary sail boat, air is blown from a fan attached to the boat. The boat

A. moves in opposite direction in which the air is blown
B. does not move
C. moves in the same direction in which air blows
D. spins around

Ans: B. does not move

## Question 13.

Light travels at the fastest speed in:

A. glass
B. water
C. hydrogen
D. vacuum

Ans: D. vacuum

## Question 14.

Of the four locations mentioned below the highest inside temperature will be attained in the pressure cooker operated with the pressure valve open

A. at sea level
B. at the top of Mt. Everest
C. at a place in a valley below sea level
D. in an aeroplane flying at a height of 10,000 m with inside pressure maintained at the sea level

Ans: C. at a place in a valley below sea level

## Question 15.

Optical fibre works on the

A. principle of refraction
B. total internal reflection
C. scattering
D. interference

Ans: B. total internal reflection

## Question 16.

Rainbow is due to

A. absorption of sunlight in minute water droplets
B. diffusion of sunlight through water droplets
C. ionisation of water deposits
D. refraction and reflection of sunlight by water droplets

Ans: D. refraction and reflection of sunlight by water droplets

## Question 17.

Railway tracks are banked on curves

A. necessary centrifugal force may be obtained from the horizontal component weight of the train
B. to avoid frictional force between the tracks and wheels
C. necessary centripetal force may be obtained from the horizontal component of the weight of the train
D. the train may not fly off in the opposite direction

Ans: C. necessary centripetal force may be obtained from the horizontal component of the weight of the train

## Question 18.

Radio telescopes are better than optical telescopes because

A. they can detect faint galaxies which no optical telescope can
B. they can work even in cloudy conditions
C. they can work during the day and night
D. All of the above

Ans: D. All of the above

## Question 19.

Light from the star, Alpha Centauri, which is nearest to the earth after the sun, reaches the earth in

A. 4.2 seconds
B. 42 seconds
C. 4.2 years
D. 42 years

Ans: C. 4.2 years

## Question 20.

Stars which appear single to the naked eye but are double when seen through a telescope are

A. novas and supernovas
B. binaries
C. asteroids
D. quasars

Ans: B. binaries

## Physics GK MCQs all set

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