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JEE Main Physics question

PhysicsWork, Energy and PowerJEE Main

A machine, which is 75 percent efficient, uses 12 joules 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

Useful (PE gained) work = 75% of 12 J = 9 J = mgh ⟹ h = 9/(1×10) = 0.9

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Question ID VK-153972