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## Homework Statement

The combination of an applied force and a frictional force produces a constant total torque of 39.9Nm on a wheel rotating about a fixed axis. The applied force acts for 4.5s, during which time the angular speed of the wheel increases from 3 rad/s to 12 rad/s. The applied force is then removed. The wheel comes to rest in 72s.

A. What is the moment of inertia of the wheel? Answer in units of kgm^2

B. What is the magnitude of the frictional torque? Answer in Nm

C. What is the total number of revolutions of the wheel?

## Homework Equations

[tex]\sum[/tex][tex]\tau[/tex] = I(moment of inertia) * [tex]\alpha[/tex]

## The Attempt at a Solution

A. 39.9 = 2I

I = 19.95

That is correct.

B. T = (19.95)(9/72) = 2.49375

That is incorrect. What am I doing wrong?

C. I need some help, do not know where to start.

Thanks in advance.

Sorry if the equations look bad. This the first time I am using Latex and I still don't know exactly how to use it correctly.