Physics (10th Edition)

Published by Wiley
ISBN 10: 1118486897
ISBN 13: 978-1-11848-689-4

Chapter 9 - Rotational Dynamics - Check Your Understanding - Page 239: 15


$KE_r$ is greater for axis B.

Work Step by Step

Rotational kinetic energy is calculated by $$KE_r=\frac{1}{2}I\omega^2=\frac{1}{2}\sum MR^2\omega^2$$ In both cases, the total mass $\sum M$ is the same. However, in the case of axis B passing through one corner of the triangle, there are more masses farther away from the axis than in the case of axis A. Therefore, $R_B\gt R_A$ Because $\omega$ is the same for both cases, $KE_r$ is greater for axis B.
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