Physics (10th Edition)

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

Chapter 9 - Rotational Dynamics - Problems - Page 244: 15


The magnitude of $\vec{M}$ is $1196N$ and its direction is to the left.

Work Step by Step

There are 2 forces acting on the arm: - The horizontal force $M$ that the person's flexor exerts on forearm, pointing to the left. - The tension in the test apparatus, which reads $T=190N$. It points to the right. Choose the rotation axis to be at the elbow joint. - For $M$, the lever arm is $0.054m$. - For $T$, the lever arm is $0.34m$. Because the arm is in equilibrium, $$0.054M=0.34T$$ $$M=\frac{0.34T}{0.054}=1196N$$
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