Question

A fixed pulley is driven by a 100 kg mass falling at a rate of 8.0 m in 4.0 s. It lifts a load of 75.0 kgf. Calculate the efficiency of the pulley.

Answer 1

Load pulled by the pulley is L = 75 × 10 = 750 N

Therefore, M.A. is

M.A. = `"L"/"E" = 750/1000 = 0.75`

When the effort moves by a distance d downwards, the load moves by the same distance upwards. So, V.R. = 1

Hence, efficiency is

η = `"M.A."/"V.R." = 0.75/1` = 0.75  (or 75 %)