Law of Conservation of Energy
Energy can neither be created nor be destroyed. It can only be converted from one form to another. The total amount of energy in the Universe thus remains constant.
Some form of energy or the other is needed to do work. This energy can be on account of position of the system, or an object, and is known as potential energy. Whereas, kinetic energy is the energy that a system, or a body possesses, owing to its relative motion. The total energy of the system is the sum of its potential and kinetic energy which is known as the mechanical energy of the system.
The planets revolving around the sun, the atoms spinning around the nucleus, a soccer ball that is moving or even a fish swimming are some of the examples of systems that possess mechanical energy.
Mechanical energy can be used to do work. To follow in this article are explanations of a few examples of how mechanical energy can be converted to other forms of energy as well as how other forms of energy are converted to mechanical energy to do work.
Mechanical Energy Examples
A Ball Placed on a Table
When a ball is placed on a table, it is at rest. It will have potential energy due to the height of the ball from the ground. Now if the ball were to fall off from the table, the potential energy will begin to convert into kinetic energy. Their sum, however, will remain constant and it will be the total mechanical energy of the system. Just before the ball touches the floor below, the total potential energy of the system will reduce down to zero and it will have only kinetic energy.
A hydroelectric plant is an example of conversion of mechanical energy to electrical energy. The mechanical energy of the water falling down from a waterfall is used to rotate the turbines that are present at the bottom of a waterfall. The rotation of these turbines is used to generate electricity.
A Dart Gun
A dart gun can store mechanical energy in the form of elastic energy. The dart gun has a spring that can store the elastic energy when it is in a compressed position. This energy, when the spring relaxes, causes the dart to move. Thus converting the elastic energy of spring to kinetic energy of the dart in motion.
Some other examples of conservation of mechanical energy are:
In the examples where mechanical energy is stored, it is stored in the form of potential energy. There are also instances when a body has both types of energies simultaneously. Like a satellite that is orbiting the Earth will have potential energy because of its position from the surface of the Earth as well as kinetic energy on account of its relative motion with respect to the planet.