Chapter 15, Problem 22A

Suppose you're playing catch with a friend in a moving train. When you toss the ball in the direction the train is moving, how does the speed of the ball appear to an observer standing at rest outside the train? (Does it increase or appear the same as if the observer were riding on the train?)

To determine

The speed of ball as per observer standing at rest outside the train.

Explanation of Solution

Introduction:

The relative velocity is the velocity of a body with respect to another body in its rest frame.

When the ball is tossed in the train, the speed of the ball would be higher as per observer outside the train in its rest frame. This is because the ball would have additional velocity of the train. From within the train, the observer would see the ball’s own speed as it is in the same frame as the ball is.