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Q4. A screw-jack has a square thread with a mean diameter of 60 mm and a pitch of 8 mm. The lifting cap has an outer diameter of 90 mm and an inner diameter of 60 mm. The coefficient of friction at all contact surfaces is a constant 0.15 when a load of 5600 N is lifted or lowered using a bar that is 1.5 m in length.

Calculate the difference in the applied force required to lift and lower the load. (16)