1. What does the equationE =mc² mean?

2. Suppose a person riding on top of a freight car shines a searchlight beam in the direction in which the train is traveling. Compare the speed of the light beam relative to the ground when:

a. The train is at rest.

b. The train is moving.

3. How does the behavior of the light beam differ from the behavior of a bullet fired in the same direction from the top of the freight car?