Physics: Principles with Applications (7th Edition)

Published by Pearson
ISBN 10: 0-32162-592-7
ISBN 13: 978-0-32162-592-2

Chapter 8 - Rotational Motion - Questions: 4

Answer

Because of the distribution of mass around your axis of rotation.

Work Step by Step

When you move your hands from in front of you to behind your head, you increase the moment of inertia of the upper half of your body. This is because you have moved mass away from the axis of rotation. The larger moment of inertia means that it is harder for your abdominal muscles to rotate the upper half of your body.
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