The following particulars refers to a screw jack shown in figure below:
Vertical load on the screw W=20,000 N
Force applied at the lever end whose length l = 80cm
Mean radius of the screw
r = 2.5cm
Pitch of the screw p = 1cm
Mean radius of contact surface between swivel and head
rm = 4cm
Coefficient of friction between screw thread and bearing
m1 = 0.15
Coefficient of friction between the swivel head and bearing m = 0.1
Determine:-
(i) The force on the lever end required while raising and lowering the load.
(ii) The efficiency of the screw jack in both cases.
