Physics: Principles with Applications (7th Edition)

Published by Pearson
ISBN 10: 0-32162-592-7
ISBN 13: 978-0-32162-592-2

Chapter 6 - Work and Energy - Misconceptual Questions: 7

Answer

Choice B.

Work Step by Step

The kinetic energy is proportional to the square of the speed, i.e., $KE = \frac{1}{2} mv^{2}$. Moving at 60 km/h, the car has 4 times the kinetic energy that it does moving at 30 km/h. In other words, it takes four times as much work to accelerate the car from 0 to 60 km/h as it takes to accelerate the car from 0 to 30 km/h. From that, we conclude that going from 30 to 60 takes three times the work as going from 0 to 30.
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