b. A screw jack has a single start thread of pitch P mm and a turning handle of length L mm. The efficiency of the jack as a lifting device is %. Calculate: i. ii. the force required at the handle to lift a load of W tonne the work done on the W tonne load when lifting it through a height of h mm For MA. P7b data Screw Bar pitch Length Load Height Efficiency P L W h % 1 mm mm tonne mm 27 25 300 2.2 220 2 31 20 400 1.4 200 3 33 24 350 1.1 180 4 36 32 450 0.9 170