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

answer: strength i guess

explanation:

no. dot product   =0 when vecs at right angles