A woman sits on a spinning piano stool with her arms extended. When she folds her arms, which of the following occurs? Question
5 options: She increases her moment of inertia, thereby decreasing her angular speed. She decreases her moment of inertia, thereby increasing her angular speed. She decreases her moment of inertia, thereby decreasing her angular speed. She increases her moment of inertia, thereby increasing her angular speed.
The correct option is that (She decreases her moment of inertia, thereby increasing her angular speed.)
Explanation:
When an object is in circular motion, the vector that describes it is known as angular momentum. Angular momentum is conserved or constant when an object is spinning in a closed system and no external torques are applied to it. An example of conservation of angular momentum is seen when a woman is sitting on a spinning piano stool with her arms extended. Her angular momentum is conserved because the net torque on her is negligibly small as the friction is exerted very close to the pivot point.
When she folds her arms,her rate of spin increases greatly decreasing her moment of inertia. The work she does to pull in her arms results in an increase in rotational kinetic energy( that is, increase in her angular speed). I hope this helps, thanks!
