Screw jack has a thread with a pitch of 5mm and diameter of 25mm

The coefficient of friction is 0.25

1) Calculate the efficiency when a load is raised

2) Then, Calculate the effort needed to raise a load of 6kN with a handle 500mm long.

A lead screw and saddle arrangement is used to lift a load of 200kg.

The square thread has a pitch of 8mm and a diameter of 30mm.

The coefficient of friction is 0.2.

1) Calculate the torque needed to rotate the screw on raising and lowering