Understanding Angular Momentum & Energy in Rotational Motion

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Homework Help Overview

The discussion revolves around the concepts of angular momentum and energy in the context of rotational motion, specifically examining a scenario where a man rotates while holding weights and changes his moment of inertia by pulling his arms in.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants explore the relationship between angular momentum and kinetic energy, questioning how energy is conserved or transformed during the motion. They also inquire about the forces at play and the source of energy when the moment of inertia changes.

Discussion Status

The discussion is ongoing, with participants sharing their thoughts and seeking clarification on the mechanics involved. Some guidance has been provided regarding the work done by the force when the arms are pulled in, but there is no explicit consensus on the overall energy transformation process.

Contextual Notes

Participants reference a specific example from a physics textbook, indicating that the problem is situated within a formal educational context. There are also indications of language barriers affecting communication.

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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