Calculating Moment of Inertia for a Pulley with Attached Mass

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SUMMARY

The discussion focuses on calculating the moment of inertia for a pulley with an attached mass of 1.65 kg and a radius of 4.65 cm, experiencing a constant acceleration of 2.40 m/s². The correct approach involves using the equations I = mr² and Torque = I * alpha, where Torque is derived from T = m * g * r. The user initially attempted to calculate the moment of inertia incorrectly by only squaring the radius and multiplying by the mass, leading to an incorrect answer. Ultimately, the user discovered a different set of equations that yielded the correct moment of inertia.

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  • Knowledge of torque calculations
  • Basic algebra for manipulating equations
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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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