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 ossilate why does the bob eventually come to rest

Answer 1

In physics, the law of conservation of energy states that the total energy of an isolated system remains constant and that energy can neither be created nor destroyed; rather, it can transform from one form to another.

When a pendulum moves from its main position to either of its extremes,it rises through a height above the mean level.At this point,the K.E of the bob changes into P.E..As it moves back to the main position,its P.E decreases progressively and K.E. increases.As the bob reaches the main position,it has only K.E.This process is repeated as long as the bob oscillates.

The bob eventually comes to rest because the air resistance resists its motion and the pendulum loses its K.E. to overcome this friction and stops after sometime.

The law of conservation of energy isn't violated as the energy lost by the pendulum is gained by its surroundings.

Answer 2

When bob is at rest, it has height h ,therefore it has potential energy starts increasing but when it starts coming back to mean position, its height starts decreasing as h is decreasing but its velocity increases, therefore, the bob carries kinetic energy 1/2 mv² .. so there is change of form of energy