JEE Main Physics question
A machine which is 75% efficient, uses 12 J of energy in lifting up a 1 kg mass through a certain distance. The mass is then allowed to fall through that distance. The velocity at the end of its fall is (in ms⁻¹)
Answer: (C)
Solution
(Same as Q207.) Useful PE gained = 0.75×12 = 9 J, converting fully to KE on falling: ½(1)v² = 9 ⟹ v = √18 ms⁻¹.