Question

How would a stationary observer view a clock on a train that is moving at close to the speed of light, compared with an identical clock sitting next to the observer?

A. The clock on the train would appear wider and run faster.

B. The clock on the train would appear narrower and run faster.

C. The clock on the train would appear narrower and run more slowly.

D. The clock on the train would appear wider and run more slowly.

Answer 1

C. The clock on the train would appear narrower and run more slowly

Explanation:

This is a good example of the length contraction and time dilation, according to special theory of relativity.

A vehicle that moves very fast, at speeds close to the speed of light, will appear smaller to a stationary observer. This is called length contraction

A clock in the moving vehicle will run slowly, compared to the clock in the stationary reference frame. This is time dilation.

For example, if clock with the stationary observer reads a duration of 6 hours, the identical clock on the moving train reads about 4 hours (slower).

Answer 2

The correct option is C.
According to the special theory of relativity, the speed of a moving clock depend on the speed at which it is travelling. A clock that is travelling very fast will have a slower passage of time while the one that is slower will have a faster passage of time. In the question given above, the clock sitting next to the observer will be very fast because it is not in motion while the clock that is on the training will be slower and it would appear narrower because it is moving away from the observer.