Question

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 ​

Answer 1

ANSWER:

Law of conservation of energy state that energy can neither be created nor be destroyed it can only be converted into one form to another form.

Now, let us consider a pendulum in which to and fro motion will take place. When pendulum bob moves from its rest position (mean position) to another extreme position its kinetic energy will be converted into potential energy when it is raised at some height 'h'. Now when it come back to its mean position, then its potential energy will be converted into kinetic energy and this phenomenon will take place again and again.

The bob will eventually come to rest due to the frictional resistance offered by air on the surface of bob and pendulum loses its kinetic energy to overcome this friction and finally comes to rest.

The law of conservation of energy is not violated because the kinetic energy loss by pendulum to overcome the friction is gained by surrounding, So total energy of system will remain conserved.

Answer 2

Answer:

When the pendulum bob is pulled ( says towards left), the energy supplied is stored in it is the form of PE on account of it's higher position. When the pendulum is released so that it starts moving towards right, then it's PE changes into KE such that in mean position, it has maximum KE, and Zero PE. As the pendulum moves towards extreme right, its KE changes into and zero KE. When it moves from this extreme position to mean position, it's PE again changes to KE. This illustrates the law of conversation of energy. Eventually, the bob comes to rest, because during each oscillation a part of the energy possessed by it transferred to air and in overcoming friction at the point of suspension. Thus, the energy of the pendulum is dissipated in air.

The law of conversation of energy is not violated because the energy merely changes it's form and is not destroyed.

Explanation:

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