Understanding Angular Momentum & Energy in Rotational Motion

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When a man holding weights extends his arms and rotates, pulling his hands towards his stomach increases his angular velocity due to the conservation of angular momentum. This action decreases his moment of inertia, as the radius (r) in the equation for moment of inertia (I = mr²) becomes smaller. The change in kinetic energy (KE) occurs because the force exerted while pulling his arms in does work on the system. The source of energy for this increase in angular velocity is the work done by the muscles in his arms. Understanding these principles is crucial for grasping concepts in rotational motion and energy conservation.
Ali Asadullah
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Suppose a man is holding his arms extended in with some masses in each hand. He is set rotating about a vertical axis . If he pulls his hands toward his stomach then according to law of conservation of angular momentum there is an increase in his angular velocity. Also there is a change in his KE from where the energy comes or go? Also We have work=Change in KE
which force does work in dis case?
 
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Actually this is question in University Physics H D Young 10 edition Example 10-13.
 
What force do you think does work in this case? Where do you think the energy comes from?
 
Dear i don't know that is why iam asking from u people.
 
Ali Asadullah said:
Dear i don't know that is why iam asking from u people.

How would he decrease his moment of inertia in this case?
 
Dear moment ov inertia is mr^2, when he pulls his hands towards his stomach r^2 decreases and hence Moment ov inertia decreases.
 
I have asked ma Physics teacher and he replied that the force with which he pulls his hands towards his body actully does work.
Soory for any Grammatical mistake as English is not ma mother tongue.
 
Ali Asadullah said:
I have asked ma Physics teacher and he replied that the force with which he pulls his hands towards his body actully does work.
Absolutely.
 

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