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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 gravityThe 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

Answer»

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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