Physics Technology Update (4th Edition)

Published by Pearson
ISBN 10: 0-32190-308-0
ISBN 13: 978-0-32190-308-2

Chapter 8 - Potential Energy and Conservation of Energy - Problems and Conceptual Exercises - Page 247: 31

Answer

(a) $15\frac{m}{s}$ (b) $43m$

Work Step by Step

(a) We know that $\frac{1}{2}mv_i^2+mgh=\frac{1}{2}mv_f^2+0$ This can be rearranged as: $v_i=\sqrt{v_f^2-2gh}$ We plug in the known values to obtain: $v_i=\sqrt{(29)^2-2(9.81)(32)}$ $v_i=15\frac{m}{s}$ (b) According to the law of conservation of energy $K.E_{max}+U_{max}=K.E_f+U_f$ $\implies 0+mgy_{max}=\frac{1}{2}mv_f^2+0$ This simplifies to: $y_{max}=\frac{v_f^2}{2g}$ We plug in the known values to obtain: $y_{max}=\frac{(29)^2}{2(9.81)}$ $y_{max}=43m$
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