If mass 'm' is dropped from height 'h' vertically, 'f' is the force of friction during downward motion and 'v' is the velocity at bottom, following will hold:
Correct answer: D. mgh=½mv²+fh
- A. ½mv²=mgh+fh
- B. mgh=½mv²-fh
- C. fh=mgh+½mv²
- D. mgh=½mv²+fh
Explanation
Throughout the course of this fall, we would be having the gravitational potential energy converted to kinetic energy and the energy needed to overcome friction. Thus mgh (being the maximum gravitational potential energy) equals the maximum kinetic energy (at the bottom of the fall) and the energy utilized to overcome friction.
This question appeared on the UHS MDCAT 2017 paper, which you can sit online with every answer explained.
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The work-energy theorem states that the net work done on an object equals its change in kinetic energy. Questions involve positive and negative work, variable forces and force-displacement graphs, acceleration or deceleration, and the difference between this theorem and conservation of mechanical energy, which also requires attention to potential energy and non-conservative work.
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