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Illustrate the law of conservation of en...

Illustrate the law of conservation of energy by discussing the energy changes which occur when we draw a pendulum bob to one side and allow it to oscillate. Why does the bob eventually come to rest? What happens to its energy eventually? Is it a violation of the law of conservation of energy?

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A simple pendulum consists of a spherical metal bob suspended by a thread from a rigid supprts. .A. is the mean position of the pendulum. As the bob is displaced to end .C., it gains potential energy. As it is released from rest (position .C.), its kinetic energy begins to increase. At the intermediate position .B. the energy is partly kinetic and partly potential. At mean position .A., the energy is totally kinetic. At the end .D. again the energy becomes totally potential. The transformation of energy goes on and the pendulum oscillates. Total mechanical energy remains constant at all points.
The energy of the pendulum is gradually used in doing work against the force of friction at the point of suspension and also against friction of air. With the passage of time, energy of the pendulum goes on decreasing and finally become zero. So the bob eventually comes to rest.
There is no violation of the law of conservation of energy.
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