Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Published by Pearson
ISBN 10: 0321740904
ISBN 13: 978-0-32174-090-8

Chapter 2 - Kinematics in One Dimension - Exercises and Problems: 63

Answer

The speed is 5.7 m/s just as the light turns green.

Work Step by Step

The car moves 20 meters in 1.0 second. Then the car needs to travel 180 meters in 14 seconds. We can find the speed after slowing for 14 seconds as: $v_{ave}~t=x$ $\frac{v+v_0}{2}~t = x$ $v = \frac{2x}{t}-v_0$ $v = \frac{(2)(180~m)}{14~s}-20~m/s$ $v = 5.7~m/s$ The speed is 5.7 m/s just as the light turns green.
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