1. The problem statement, all variables and given/known data 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? http://i241.photobucket.com/albums/ff4/alg5045/p13-69.gif 2. Relevant equations 3. 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.