The 1.6kg, 20cm diameter disk in the figure below is spinning at 240rpm. How much friction force must the brake apply to the rim to bring the disk to a halt in 3.5s?
The Attempt at a Solution
I know a free body diagram should be drawn for the disk to take all of the forces into account. I know there's the weight pulling down and the frictional force is acting to the right, but I don't know how to set up a solvable equation.