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Rotating Wheel - Torque and Moment of Inertia

by kd001
Tags: inertia, moment, rotating, torque, wheel
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kd001
#1
Nov12-09, 02:56 PM
P: 43
1. The problem statement, all variables and given/known data

A wheel free to rotate about its axis that is not frictionless is initially at rest. A constant external torque of 50N_m is applied to the wheel for 20s, giving the wheel an angular velocity of 600rev/min. The external torque is the removed and the wheel comes to rest 120s later. Find the moment of inertia of the wheel.


2. Relevant equations

τ=Iα
α= ω/t


3. The attempt at a solution

ω=62.83rad/s
α_1=62.83/20=3.14rad per s^2
α_2=(-62.83)/120=-0.52rad per s^2
50- τ_f=Iα_1
τ_f=I(α_2)
50=I(α_1+ α_2 )
I=50/(3.14-0.52)
I=19.1

The answer should be around 27 but whatever I did I could not get that.

Thanks
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