An apple gives 21 kJ energy to a boy. How much height he ca…

Physics Work, Energy, Power and Collision Potential Energy and Mechanical Energy Conservation MCQ (Single Correct)

An apple gives 21 kJ energy to a boy. How much height he can climb by using this energy. If his efficiency is 28%? (mass of boy 40 kg)

22.5 m

15 m

10 m

5 m

Text Solution

Verified by Experts

The correct answer is:

Here: Energy of one apple = 2112 J

= 2112 J

= 21 × 103 J

Efficiency of the boy = 28% = 0.28

= 28% = 0.28

Mass of the boy m = 40 kg

m = 40 kg

Here the actual energy consumed by the boy is given by as

= 0.28 × 21000 = 5880 J ...

and the energy consumed by the boy in climbing h meter height is given by

= m g h = 40 × 9.8 × h J ...

Equating equations and we get

40 × 9.8 × h = 5880 J

h = = 15 m

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