Have you ever observed a ball when thrown vertically upward with certain force? It goes to a certain height and comes back to the ground when it strikes the ground it bounces back in upward direction once again. Do you know what different forms of energy are involved here and what energy conversion is going on in this motion? Before understanding this, let us try to understand what Conservation of Energy is.
For an isolated system, the total amount of energy remains conserved. In other words we can say that energy can neither be created nor destroyed, it can only be changed from one form to the other. Conservation of energy tells that the total amount of energy remains unchanged. However, during a process or activity one form of energy may get changed to the other form, but if you calculate the total amount of energy, it will remain conserved.
Conservation of Energy when Ball Going Up
For an example If a is ball thrown vertically upward. Using our muscle energy, we provide some kinetic energy to ball and ball starts moving with this kinetic energy in upward direction. As the ball goes up its kinetic energy starts converting into potential energy. As a result the kinetic energy of the ball start decreasing and potential energy of the ball starts increasing. Due to decrease in kinetic energy, the velocity of the keeps on decreasing and finally at one point it becomes zero. This is the highest point up to which ball can go. At this point the total kinetic energy of the ball has converted into potential energy.
Thus at highest point, ball has no kinetic energy and highest potential energy. It is interesting to know that the potential energy as this point is equal to initial kinetic energy of the ball. This is as per the conservation of energy because kinetic energy is converted into potential energy but total amount of energy remains same.
Conservation of Energy when Ball Falls Down
Now ball starts falling down with this potential energy and as it falls down under gravity, its potential energy starts converting into kinetic energy. As a result the potential energy decreases and kinetic energy increases and velocity of the ball goes on increasing. The moment when ball strikes the ground, all its potential energy is converted into kinetic energy and once again due to conservation of energy, this energy is equal to the potential energy at the top as well as to the initial kinetic energy.