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Q4. A screw jack consists of single start, square form screw thread of 8 mm pitch and a mean diameter of 100 mm. The mean diameter of the bearing surface under the loading cap is 300 mm and the effort handle has an effective operating length of 600 mm from the axis of the screw thread. The coefficient of friction are 0.15 and 0.25 at the square thread and the bearing surface respectively.

Calculate EACH of the following:

(a) The minimum force required to raise a mass of 300 kg. (10)

(b) The minimum force required to lower the same mass. (6)