Calculating Moment of Inertia for a Pulley with Attached Mass

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Homework Help Overview

The problem involves calculating the moment of inertia for a pulley with an attached mass, where the mass falls with a specified acceleration. The context includes the mass, the radius of the pulley, and the conditions of negligible friction.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss various attempts to calculate torque and moment of inertia, including using the formula I=mr^2 and exploring the relationship between torque and angular acceleration. Questions arise regarding the correctness of these approaches and the equations used.

Discussion Status

The discussion reflects a mix of attempts and clarifications, with some participants expressing uncertainty about their methods. One participant mentions finding a solution using a different set of equations, indicating a potential shift in understanding, but no consensus on the correct approach has been reached.

Contextual Notes

Participants are navigating through the implications of using different equations and the assumptions underlying their calculations. There is an acknowledgment of previous attempts yielding incorrect results, prompting further exploration of the problem.

Keithkent09
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Homework Statement


A 1.65 kg mass is attached to a light cord that is wrapped around a pulley of radius 4.65 cm, which turns with negligible friction. The mass falls at a constant acceleration of 2.40 m/s2. Find the moment of inertia of the pulley.

Homework Equations


I=mr^2
Torque=I*alpha


The Attempt at a Solution


I tried to just square the radius given and multiply it by the mass but that did not work. I also tried to find the Torque using T=mgr. And then divided that number by the acceleration/radius in order to get the angular acceleration.
 
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Keithkent09 said:
I also tried to find the Torque using T=mgr. And then divided that number by the acceleration/radius in order to get the angular acceleration.

So what did that give you?
 
It gave me the wrong answer. I guess that is not the correct way to find the torque
 
Keithkent09 said:
It gave me the wrong answer. I guess that is not the correct way to find the torque

That should be the correct way to do it, post your work.
 
I figured it out using a different set of equations. Thanks for your help though, sorry to waste your time.
 
Keithkent09 said:
I figured it out using a different set of equations. Thanks for your help though, sorry to waste your time.

What equations did you use by chance?
 

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