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
Answers
Ans. In the case of pendulum energy in the Bob at any instant of time, can be either potential
energy (P.E) or kinetic energy (K.E) or a mixture of both but its total energy at any instant of
time remains constant. This can be illustrated by below illustration in the figure.
In case of pendulum energy in the Bob at any instant of time
when the pendulum Bob is at position B.It has only potential energy(P.E) and no kinetic
energy(K.E)
As the Bob starts moving from position B to position A potential energy(P.E) decreases but
Kinetic Energy(K.E) increases
when the Bob reaches position A, there is only kinetic energy(K.e) but no potential
energy(P.E)
As Bob moves from position A to position C, potential energy(p.E) increases but kinetic
energy decreases.
when Bob reaches position C, Bob stops for a very small instant of time, At that time, Bob
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.