Physics - Study Mode

[#486] The rate of change of linear momentum of a body falling freely under gravity is equal to it's ________ ?
Correct Answer

(B) Weight

Explanation

Solution: Rate of change of impulse equals the force . In case of freely falling body the only force is the weight.

[#487] According to the theory of relativity, which of the following always remains constant ?
Correct Answer

(D) Velocity of light

Explanation

Solution: The theory of relativity, or simply relativity, generally encompasses two theories of Albert Einstein: special relativity and general relativity. Concepts introduced by the theories of relativity include: Measurements of various quantities are relative to the velocities of observers. In particular, space and time can dilate. Space time: space and time should be considered together and in relation to each other. The speed of light is nonetheless invariant, the same for all observers.

[#488] In a railway track, two rails are joined end to end with a gap in between them because
Correct Answer

(D) Accidents due to expansion in summer can be avoided

Explanation

Solution: In a railway track, two rails are joined end to end with a gap in between them because accidents due to expansion in summer can be avoided.

[#489] Air coolers are more suitable for
Correct Answer

(B) Hot and dry climate

Explanation

Solution: Air coolers are more suitable for hot and dry climate.

[#490] We feel cool when we sit near the fan, this is because
Correct Answer

(C) Air vapourises the sweat on our body.

Explanation

Solution: A fan produces a feeling of comfort because our perspiration or sweating evaporates rapidly. Our body tries to cool ourselves by releasing sweat through pores of our skin. And when we sit under the fan, the sweat of our body evaporates due to directed air upon us making our body cool.