Howard J. answered • 10/12/19
Principal Mech Engr with 35+ years' on-the-job physics experience
Assume a bucket of water with a total mass of 23 kg is attached to a rope, which in turn is tied around a 0.50 m radius cylinder at the top of a well. A crank with a turning radius of 0.25 m is attached to the end of the cylinder. What minimum force directed perpendicular to the crank handle is required to raise the bucket?
(Assume the rope's mass is negligible, that the cylinder turns on friction-less bearings, and that g = 9.8 m/s2
The crank handle provides a torque T=0.25F where F is the force we are looking for.
A free body diagram will show that the tension in the rope times the cylinder radius R is equal to the torque on the cylinder. But the tension in the rope is just the weight of the bucket W=mg= 23g
W(0.5)=T=0.25F
F=2W=2(23g)=46g= 451 N
Solution: 0.45 kN
