Question

Five pulleys are arranged in the second system of pulleys. When not loaded 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 effort required to raise a load of 2kN?

(a) 500 N

(b) 400 N

(c) 495 N

(d) none of the mentioned

I have been asked this question in a national level competition.

My query is from Pulleys in division Belt, Rope and Chain Drives of Machine Kinematics

Answer 1

Correct answer is (c) 495 N

Explanation: 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.