Practice MCQ Questions and answers on Physics-GK

41

Sound travels at the fastest speed in

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

Discuss

Answer & Solution

Answer: Option A

Solution:

Sound travels fastest through solids. This is because molecules in a solid medium are much closer together than those in a liquid or gas, allowing sound waves to travel more quickly through it. In fact, sound waves travel over 17 times faster through steel than through air.

42

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

Discuss

Answer & Solution

Answer: Option C

Solution:

The raise of oil up the wick in a lamp is an example of capillary action where adhesive forces are greater than cohesive forces.

43

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

Discuss

Answer & Solution

Answer: Option C

Solution:

By definition, superconductors are substances which display zero electrical resistance when a current is supplied, and are able to propagate such a current in a circuit indefinitely.

44

Light travels at the fastest speed in:

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

Discuss

Answer & Solution

Answer: Option D

Solution:

Light travels at the fastest speed in Vacuum.

45

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

Discuss

Answer & Solution

Answer: Option C

Solution:

When a fast moving train takes a curved path, it tends to move away tangentially off the track. In order to prevent this, the curved tracks are banked on the outside to produce the necessary centripetal force required to keep the train moving in a curved path.

46

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

Discuss

Answer & Solution

Answer: Option C

Solution:

Metals are good conductor of heat.

47

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

Discuss

Answer & Solution

Answer: Option D

Solution:

3.3 km, 0.30 km.

48

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

Discuss

Answer & Solution

Answer: Option D

Solution:

Intensity of sound at a point is inversely proportional to square of its distance from the source.

49

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

Discuss

Answer & Solution

Answer: Option C

Solution:

Of the four locations mentioned below the highest inside temperature will be attained in the pressure cooker operated with the pressure valve open at a place in a valley below sea level.

50

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

Discuss

Answer & Solution

Answer: Option D

Solution:

Radio telescopes are better than optical telescopes because they can detect faint galaxies which no optical telescope can, they can work even in cloudy conditions and they can work during the day and night.