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inner08
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Homework Statement
A wheel is turning initially at 1200 turns/min and stops in 4 min because of friction. If we add a supplementary torque of 300 N*m, the wheel stops in 1 min.
a) What is the moment of inertia of the wheel?
b) What is the torque of friction?
Homework Equations
Torque = alpha * I
time = w/alpha
f = ucF
Torque = -fR
The Attempt at a Solution
I figured i'd start by converting the 1200 turns/min into rad/sec
(1200 *2pi)/60 = 126 rad/sec (this gives me angular speed - w)
Then I figured i'd find the angular acceleration using the angular speed that I just found with the time it takes to stop (in this case its 4min or 240seconds).
alpha = 126/240
= 0.525
Now at first I thought I could just substitute these in the equation Torque = alpha * I but it doesn't work out.
I then realized that they are saying that there is a SUPPLEMENTARY torque and it then stops in 1min. I thought it would then be something like "initial torque + 300 = something...". Does that make any sense?
Any help to clear this up would be appreciated!