A pulley system with IMA of 4 requires a force of 15 New Ton tol lift a load of 45 New Ton. Find the efficiency of the machine

Answer 1

output work / input work then multiply by 100 to get the efficiency.

Answer 2

Ideal mechanical advantage = 4
so
ideally 45 Newtons weight requires 45/4 = 11.25 Newtons (NOT NEW TONS, named after Issac Newton) but it took 15 Newtons
so eff = 100 * 11.25 /15 = 75%

Answer 3

45 divided by 4 which is equal to 11.25 and 100 times 11.25 divided by 15 , we can get 75%