# Moment of Inertia of a pulley

• Keithkent09
In summary, the conversation discusses finding the moment of inertia of a pulley with a mass attached to it and a light cord. The person initially tried to use the equation I=mr^2 but it did not work. They then attempted to find the torque using T=mgr and dividing it by the acceleration and radius, but it gave them the wrong answer. They ultimately found the correct solution using a different set of equations.

## 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.

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.

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?