Work Energy Theorem and Uniform Disc Problem

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Homework Help Overview

The discussion revolves around applying the work-energy theorem to a problem involving a uniform disc. Participants are examining the relationship between the moment of inertia and kinetic energy in the context of this theorem.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to identify errors in their calculations, particularly regarding the factors of 1/2 in the equations related to kinetic energy and moment of inertia. Questions about the application of the work-energy theorem are also raised.

Discussion Status

Some participants are confirming the use of the moment of inertia formula for a uniform disc and discussing the implications of the factors involved in their calculations. There is an ongoing exploration of the reasoning behind the discrepancies in the answers obtained.

Contextual Notes

Participants are working under the constraints of the work-energy theorem and are focused on the specific parameters of the uniform disc problem. There is a noted confusion regarding the application of the moment of inertia in their calculations.

theBEAST
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Homework Statement


Using work energy theorem, solve:
9rA7A.png

The Attempt at a Solution


The actual answer (3.11s) is exactly half of my answer. Does anyone know what I did wrong?
SFjXx.jpg
 
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Note that moment of inertia of a uniform disc about an axis through its centre and perpendicular to its plane is

[itex]\frac{1}{2}[/itex]MR[itex]^{2}[/itex].
 
grzz said:
Note that moment of inertia of a uniform disc about an axis through its centre and perpendicular to its plane is

[itex]\frac{1}{2}[/itex]MR[itex]^{2}[/itex].

Yup! That is what I used I believe.
 
theBEAST said:
Yup! That is what I used I believe.
There should be two factors of 1/2 - one from Iω2/2 for the KE and another from I=Mr2/2.
 

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