Problem 3

A single-threaded 25-mm power screw is 25 mm in diameter with a pitch of 5 mm. A vertical

load on the screw reaches a maximum of 5 kN. The coefficients of friction are 0.06 for the

collar and 0.09 for the threads. The frictional diameter of the collar is 45 mm. Find the over-

all efficiency and the torque to "raise" and "lower" the load.