Fundamentals of Physics Extended (10th Edition)

Published by Wiley
ISBN 10: 1-11823-072-8
ISBN 13: 978-1-11823-072-5

Chapter 8 - Potential Energy and Conservation of Energy - Problems - Page 212: 118

Answer

$P = 69~hp$

Work Step by Step

We can express the speed in units of $m/s$: $v = (80~km/h)(\frac{1~h}{3600~s})(\frac{1000~m}{1~km}) = 22.22~m/s$ We can find the resistant force: $F_r = 300+1.8~v^2$ $F_r = 300+(1.8)(22.22~m/s)^2$ $F_r = 1188.7~N$ We can find the required force: $F-F_r = ma$ $F = ma+F_r$ $F = (\frac{12,000~N}{9.8~m/s^2})(0.92~m/s^2)+(1188.7~N)$ $F = 2315~N$ We can find the required power: $P = F~v$ $P = (2315~N)(22.22~m/s)$ $P = 51,444~W$ $P = (51,444~W)(\frac{1~hp}{745.7~W})$ $P = 69~hp$
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