Fundamentals of Physics Extended (10th Edition)

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

Chapter 13 - Gravitation - Problems - Page 381: 33a

Answer

The multiple of the energy needed to escape from Earth which gives the energy needed to escape from the Moon is $~~0.0451$

Work Step by Step

We can write a general expression for the escape speed: $v = \sqrt{\frac{2GM}{R}}$ We can write a general expression for the kinetic energy required to escape: $K = \frac{1}{2}mv^2$ $K = \frac{1}{2}m(\sqrt{\frac{2GM}{R}})^2$ $K = \frac{GMm}{R}$ We can find the ration $\frac{K_M}{K_E}$, which is the ratio of the kinetic energy required to escape from the moon to the kinetic energy required to escape from the Earth: $\frac{K_M}{K_E}= \frac{\frac{GM_Mm}{R_M}}{\frac{GM_Em}{R_E}}$ $\frac{K_M}{K_E}= \frac{M_M~R_E}{M_E~R_M}$ $\frac{K_M}{K_E}= \frac{(7.36\times 10^{22}~kg)~(6.37\times 10^6~m)}{(5.98\times 10^{24}~kg)~(1.74\times 10^6~m)}$ $\frac{K_M}{K_E}= 0.0451$ The multiple of the energy needed to escape from Earth which gives the energy needed to escape from the Moon is $~~0.0451$
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