Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (4th Edition)

Published by Pearson
ISBN 10: 0133942651
ISBN 13: 978-0-13394-265-1

Chapter 4 - Kinematics in Two Dimensions - Exercises and Problems: 19

Answer

It would take 30 seconds if the person walks while the sidewalk is moving.

Work Step by Step

Let $v_w$ be the person's walking speed. Let $v_s$ be the speed of the moving sidewalk. Let $d$ be the distance traveled along the walkway. We can set up two equations of the form $v = \frac{d}{t}$ $v_w = \frac{d}{50~s}$ $v_s = \frac{d}{75~s}$ We can set up an equation for the combined speed. $v_w+v_s = \frac{d}{50~s}+\frac{d}{75~s}$ $v_w+v_s = \frac{3d}{150~s}+\frac{2d}{150~s}$ $v_w+v_s = \frac{5d}{150~s}$ $v_w+v_s = \frac{d}{30~s}$ It would take 30 seconds if the person walks while the sidewalk is moving.
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