What is Energy
We are surrounded by Energy. Energy is everywhere and it surrounds us; but we can’t touch it and also can’t measure its mass, because it is mass less. However, we can see and feel the effects of energy on many materials.
The word energy came from the Greek Energeia, meaning in or at work.
Basic concept of energy:
Energy is the ability or capability to do work; Energy cannot be created or destroyed.
We cannot create or destroyed any energy, for our use we only can change the form or state of energy from one into another.
In the language of physical science, energy means the ability or capability to do work. Work means a change in position, speed, state, or form of matter. Therefore, energy is the capacity to change matter.
According to the law of conservation of energy, the total energy of a system remains constant, though energy may transform into another form. Two billiard balls colliding, for example, may come to rest, with the resulting energy becoming sound and perhaps a bit of heat at the point of collision.
In fact, everything that happens in the universe, from the eruption of volcanoes, to the sprouting of seed, to the moving of people, takes energy. When we turn on a motor, drive a car, cook on a stove or switch on a light, we are using energy.
The amount of energy is directly proportional to the mass of body:
m is the mass,
c is the speed of light in vacuum,
E is the rest mass energy.