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Five pulleys are arranged in the second system of pulleys. When not loadwd the effort required to raise the movable block is 35N. Further wastage in friction increases the pull at the rate of 3% of the load lifted. What is the efficiency of the system at 2kN?

Five pulleys are arranged in the second system of pulleys. When not loadwd the effort required to raise the movable block is 35N. Further wastage in friction increases the pull at the rate of 3% of the load lifted. What is the efficiency of the system at 2kN? Correct Answer 80.81%

n = no. of pulleys = 5 Frictional effort at zero loading = 35N Frictional effort at 2 kN loading = 35 + 2000 x 3/100 = 95 N When the system is considered frictionless nP = W 5P = 2000 P = 400 N Hence total effort = 400 + 95 = 495 N Efficiency at this load = effort without friction/effort with friction = 400/495 x 100 = 80.81%.

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