Question

A set of pulleys is used to raise a 200 N crate 5 m. to fo this the operator applies a force of 50 N and pulls in 25 m of rope. Find the efficiency of the pulley system.
A: 50%
B: 62.5%
C: 75%
D: 80%

Answer 1

-- The output work (energy) is (200 N) x (5 m) = 1,000 Joules

-- The input work (energy) is (50 N) x (25 m) = 1,250 Joules

-- Efficiency = (useful energy output) / (energy input)

Efficiency = (1,000 J) / (1,250 J)

Efficiency  =  0.8  or  80% (D) .