The belt pulley system is in equilibrium as shown The radii

The belt pulley system is in equilibrium as shown. The radii of the pulleys are r_1 and r_2 and the radius of the drum is r. The weight of block A is p. Determine the moment M acted on pulley I. 0Neglect the weight of pulleys.

Solution

The torque generated by the weight hanging from the drum would be equal to Force x distance from the axis

That is torque = PR

Now, this torque has to be balance by the torque being generated by the belt for the system to stay in equilibrium.

Pr = Tension x R2; That is, Tension = PR/R2

Now this tension will generate, a moment about the pulley I

That moment = Tension x R1 = PR*R1/R2