Question

A mass of `50 kg` is raised through a certain height by a machine whose efficiency is `90%` , the energy spend is `5000 J`. If the mass is now released, its `KE` on hitting the ground shall be:
A. `5000 J`
B. `4500 J`
C. `4000 J`
D. `5500 J`

Answer 1

Because the efficiency of machine is `90%`, hence potential energy gained by mass
`= (90)/(100) xx energy = (90)/(100) xx 5000 J = 4500 J`
When the mass is released now, gain in `KE` on hitting the ground
= loss of potential energy =` 4500 J`