Calculus 10th Edition

Published by Brooks Cole
ISBN 10: 1-28505-709-0
ISBN 13: 978-1-28505-709-5

Chapter 15 - Vector Analysis - 15.2 Exercises - Page 1064: 74

Answer

$I_x = 0, I_y = 0$

Work Step by Step

The wire lies along $\textbf r (t) = a\cos t \textbf i + a\sin t \textbf j = x(t) \textbf i + y(t) \textbf j$ It follows that $x(t) a \cos t , y(t) = a\sin t$ $\textbf r' = -a\sin t \textbf i + a\cos t \textbf j \Rightarrow \vert \textbf r' \vert = a$ $\rho (x,y) = y = a\sin t$ $I_x = \int_C y^2\rho(x,y) ds = \int_{t=0}^{2\pi}a^2\sin ^2 t.a\sin t.\vert \textbf r' \vert dt = a^4[-\cos t + \frac{\cos ^3 t}{3}]_0^{2\pi}=0$ $I_y = \int_C x^2\rho(x,y) ds = \int_{t=0}^{2\pi}a^2\cos ^2 t.a\sin t.\vert \textbf r' \vert dt = a^3[-\frac{\cos^3t}{3}]_0^{2\pi} = 0$
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