woman sits on a spinning piano stool with arms folded. When she extends her arms
ID: 1774268 • Letter: W
Question
woman sits on a spinning piano stool with arms folded. When she extends her arms which of the following occurs? A. She increases her moment of inertia, thereby increasing her angular speed. B. She increases her moment of inertia, thereby decreasing her angular speed. C. She decreases her moment of inertia, thereby increasing her angular speed. D. She decreases her moment of inertia, thereby decreasing her angular speed. E. Her rotational kinetic energy remains constant. In the figure, cm is the location of the center of mass of the object shown. The rotational inertia about an axis Pt is Ii and the rotational inertia about an axis through P2 is 2. The rotational inertia about an axis through cm is Icm. All three axes are parallel to each other and Ri -Ro. The relationship among these moments of inertia is: 10. A) 11 = 12 > 1cm C) I,> 1> Icm E) 11 = 12 = 1cmExplanation / Answer
she increases her moment of inertia, thereby decreasing her angular speed.(option B)
Explanation
There is no external torque acting on the spining piano stoll where the woman is sitting. Thus, there is conservation of angular momentum of the woman. Angular momentum is equal to moment of inertia of the woman times its angular speed.
When she folded her arms, her moment of inertia decreases. This results in the increase of her angular speed.
On the other hand, when she extends her arms, she increases her moment of inertia decreasing her angular speed.
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