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A body having 7 kg of mass moves slowly and covers a vertical height of 14 m. What is the work done in Joules and what force causes this work? Take g = 10 m/s^2.

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A body having 7 kg of mass moves slowly and covers a vertical height of 14 m. What is the work done in Joules and what force causes this work? Take g = 10 m/s^2.

(a) 980, gravity

(b) 980, force acting opposite to gravity

(c) 1000, gravity

(d) 1000, force acting opposite to gravity

The question was asked in an interview for job.

The question is from Work-Energy Theorem topic in portion Work, Energy and Power of Physics – Class 11

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Right choice is (a) 980, gravity

The explanation: By work-energy theorem, the total work done on a body is equal to the change in the total energy. Since the body is moving slowly, the change in kinetic energy is negligible. P.E. = mgh. The change in potential energy and hence in the total energy is 980 J. Since only gravity is acting on the body, gravity is what causes the work.

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