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 11 - Work - Exercises and Problems: 36

Answer

The sprinter's average power output is 1170 watts. The greyhound's average power output is 2000 watts.

Work Step by Step

The work done by the sprinter is equal to the kinetic energy at 3.0 s. We can find the work $W_s$ done by the sprinter. $W_s = KE$ $W_s = \frac{1}{2}mv^2$ $W_s = \frac{1}{2}(70~kg)(10~m/s)^2$ $W_s = 3500~J$ We can find the sprinter's average power output; $P_{ave} = \frac{W_s}{t}$ $P_{ave} = \frac{3500~J}{3.0~s}$ $P_{ave} = 1170~watts$ The sprinter's average power output is 1170 watts. The work done by the greyhound is equal to the kinetic energy at 3.0 s. We can find the work $W_{gh}$ done by the greyhound. $W_{gh} = KE$ $W_{gh} = \frac{1}{2}mv^2$ $W_{gh} = \frac{1}{2}(30~kg)(20~m/s)^2$ $W_{gh} = 6000~J$ We can find the greyhound's average power output. $P_{ave} = \frac{W_{gh}}{t}$ $P_{ave} = \frac{6000~J}{3.0~s}$ $P_{ave} = 2000~watts$ The greyhound's average power output is 2000 watts.
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