Suppose that a person riding on the top of a freight car shines a searchlight beam in the direction in which the train is traveling.

How does the speed of the light beam relative to the ground compare to the speed of beam when the train is at rest?

same

Explanation:

Acc. to Einstien's postulate of special theory of

Relativity, Velocity of the light beam is same in all frames of references

(a) If the freight car is at rest

The frame we can assumed as Non - inertial frame of reference s

In the inertial frame of reference, velocity of the light beam has its own value as : 3 x 10^8 m/s

(b) If the freight car is moving, the frame we can assumed as Non - inertial frame of reference

In thus case also, The velocity of the light beam will also have the same value as; 3 x 108 m/s