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## Homework Statement

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.