Physics for Scientists and Engineers: A Strategic Approach with Modern Physics (3rd Edition)

Published by Pearson
ISBN 10: 0321740904
ISBN 13: 978-0-32174-090-8

Chapter 8 - Dynamics II: Motion in a Plane - Exercises and Problems - Page 212: 29

Answer

a) $\rm 24\;h$ b) $0.223\;\rm m/s^2$ c) $0\;\rm N$

Work Step by Step

a) The period of a geosynchronous satellite is 24 hours since the Earth completes one full rotation around its axis every 24 hours. $$T=\color{red}{\bf 24}\;\rm h$$ ______________________________________________ b) The free-fall acceleration at this point is the radial acceleration of the satellite which is given by $$a_r=g=\dfrac{v^2}{R_o}\tag 1$$ So, we know that the velocity of this satellite is given by $$v=\dfrac{2\pi R_o}{T}$$ Plugging into (1); $$a_r=g=\dfrac{4\pi^2 R_o^2}{T^2R_o} $$ $$ g=\dfrac{4\pi^2 R_o }{T^2 } $$ where $R_o=R_E+h$ whereas $R_E$ is earth's radius while $h$ is the satellite height. $$ g=\dfrac{4\pi^2 (R_E+h)}{T^2 } $$ Plugging the known; $$ g=\dfrac{4\pi^2 ([6.37\times 10^6]+[3.58\times 10^7])}{(24\times 60^2)^2} $$ $$g=\color{red}{\bf 0.223}\;\rm m/s^2$$ ______________________________________________ c) Since the satellite is at a constant height and orbiting the Earth at a constant speed, it is under an endless free-fall process which means that its weight is zero. Also, there is no normal force exerted on the satellite, so its wright is zero. $$W=\color{red}{\bf 0}\;\rm N$$
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