Aclock on a moving train runs an identical clock at rest. a. faster than
b. slower than
c. at the same speed as
d. it depends on which direction the train is moving.

A.Faster than

Explanation:

Due to the Doppler effect which states that there is a change in frequency because of the relative speeds of two bodies time dilation takes place. For light the relative difference in velocity between the observer and the source needs to be considered.

Time dilation is the phenomenon where time flows differently for two bodies having different to each other. Time dilation has been verified by the readings of the satellite navigation systems.

Where

Δt' = Time elapsed of a moving body

Δt = Time elapsed when the body is stationary

v = Velocity of the moving body

c = Speed of light

As, v is always less than c, Δt' will always be greater than Δt. This means that more time has elapsed for the body in motion.

Hence, the clock in motion will be faster than an identical clock at rest.

b. a lightning bug, plug of grass, and a worm