Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 6 - Work and Energy - Problems - Page 167: 38



Work Step by Step

The skateboarder reaches his highest point when his speed equals $0$. Reaching the highest point from his initial position means there is a decrease in KE: $$\Delta KE=\frac{1}{2}m(v_f^2-v_0^2)$$ As shown, his final speed $v_f=0$ and $v_0=5.4m/s$. So, $$\Delta KE=\frac{1}{2}m(-29.16)=-14.58m$$ This decrease in KE means an increase in PE. In detail, $$\Delta PE=-\Delta KE=14.58m$$ $$mgh=14.58m$$ ($h$ is the difference in height as shown in the drawing) $$gh=14.58$$ $$h=\frac{14.58}{9.8}=1.49m$$
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