Engineering Statics


A 25 lb. weight is suspended from a lightweight rope wrapped around the inner cylinder of a drum. A brake arm is pressed against the outer cylinder of the drum by a hydraulic cylinder. The coefficient of friction between the brake arm and the drum is 0.40. Determine the smallest force in the hydraulic cylinder necessary to prevent motion.

The FBD of the cylinder is drawn.
The moment equation about point A is written.
This allows us to find the normal force.
The FBD of the brake arm is drawn.
The moment equation is written about point C for the brake arm.