University Physics with Modern Physics (14th Edition)

Published by Pearson
ISBN 10: 0321973615
ISBN 13: 978-0-32197-361-0

Chapter 7 - Potential Energy and Energy Conservation - Problems - Exercises - Page 229: 7.5

Answer

(a) v = 24.0 m/s (b) v = 24.0 m/s (c) With air resistance, part (b) would give a higher speed than part (a).

Work Step by Step

(a) $K_2 = K_1 + U_{grav}$ $\frac{1}{2}mv_2^2 = \frac{1}{2}mv_1^2+mgh$ $v_2^2 = v_1^2+2gh$ $v_2 = \sqrt{v_1^2+2gh}$ $v_2 = \sqrt{(12.0~m/s)^2+(2)(9.80~m/s^2)(22.0~m)}$ $v_2 = 24.0~m/s$ (b) We can do the same calculation as part (a) to find that the speed of the ball just before striking the ground is 24.0 m/s (c) Since the path of the ball in part (a) follows a longer distance, the opposing force of air resistance will remove more energy from the ball. Thus, with air resistance, part (b) would give a higher speed than part (a).
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