# Moment of Inertia/Torque Question

The combination of an applied force and a frictional force produces a constant torque of 34 N.m on a wheel rotating about a fixed axis. The applied force acts for 9.1s, during which time the angular speed of the wheel increases from 0 to 16 rad/s.

a)What is the moment of inertia of the wheel?

If the applied force is removed, the wheel comes to a stop in 73s.

b)What is the frictional torque?

c)How many revolutions does the wheel make during the entire 82s interval?

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mjsd
Homework Helper
first you may want to identify some potentially useful formulas or concepts

Well torque= moment of inertia X angular acceleration....but how do u get angular acceleration if you dont know the radius??

I figured out moment of inertia, but is it the same value to use when you are trying to get frictional torque??

This problem looks so familiar. This might be random, but you don't happen to be in Dr. Turner's class?

yeah...this homework has really been giving me problems. i just want to finish. any help would be nice. its always good to have extra help from other people in the class

lol what a coincidence. I got part a and b, but c I'm just lost. Wait till you look at HW 24...it's a killer I just wanna shoot myself in the head.
For part A, use that equation Torque = mr^2 x acceleration.
You know the torque...for acceleration just take 16/9.1...plug those values in...and you are left with mr^2, which is the moment of inertia.
For part B, apply the kinematics equation...wf= w0 + at, find the acceleration, and plug it into Torque = mr^2 x a.

but for this question u aren't given a radius. i need q15 on hw 23 (part b)...for part a i did torque= I x angular acceleration and i got it right like you said....

for part b...how do i do it? i get what you are saying...but it says the wheel comes to REST after 73 seconds.. so if u do the kinematics equation wf=wo + at, wouldn't wf be zero?? how do u calc that??

sorry i know you're busy w/ hw 24 i just really wanna do this one before the 2am cutoff

it's okay,
set wf = 0 and w0 = 16, and t = 73. solve for a, which sould be a negative #.

Thanks!!! if i get q16 ill let u know...i can't seem to figure it out either...i hate to bug u but how did u figure out question 18 about the velocity of the wheel?? i got 17 but i dont know how to do number 18. please let me know...i haven't answered very many questions on this hw

AIM me...Sherry22