Disk D turns with a constant clockwise angular
velocity of 30 . Disk E has a weight of 60 lb and is
initially at rest when it is brought into contact with D.
Determine the time required for disk E to attain the same
angular velocity as disk D. The coefficient of kinetic
friction between the two disks is 0.3 . Neglect the
weight of bar BC.
2. Relevant equation
Summation of forces and moments.
The Attempt at a Solution
I am confused with the direction of friction. In my calculations, the friction points to the left because the velocity where the disk meets points to the right; which resulted to a wrong answer. However, the correct free body diagram is shown above.