Energy

Energy :- It is the capacity or ability of work done by a body.

• It is a scalar quantity.
• Its unit is joule and dimension is [M^1L^2T^-2].
• It has following types-

1. Internal Energy - It is the energy of system due to its atom or molecules.
2. Mechanical Energy - It is the sum of kinetic and mechanical energy of system.
   
   
   
   
   
   
3. Sound Energy - It generate the sensitivity in ear drums. It is required to listen voice.
4. Light Energy - It generate the sensitivity in eyes. It is required to watch object.
5. Electrical Energy - It is due to flow of electrons in any conductor.
6. Solar Energy - It is obtain from Sun light.
7. Chemical Energy - It is generate due to chemical reactions.
8. Nuclear Energy - It is due to nuclear reactions like Nuclear fission (Atom Bomb), Nuclear fusion (Hydrogen Bomb).
9. Thermal Energy - It is due to heat (temperature)  of any object.
10. Gravitational Energy - It is the work done by earth to attract any object.

Kinetic Energy - It is due to motion of body (object).
example - Wind mills work on the kinetic energy of air.

Let an object of mass m is in rest(initial velocity u=0). When F force applied on it then it accelerated by a with velocity v and displacement s.
by using third equation of motion
v^2-u^2 = 2as
since u = 0
so v^2 = 2as
a = v^2/2s
since F = ma
so F = mv^2/2s
and work W = F.s
W =  (mv^2/2s).s
W = mv^2/2
This work is stored as kinetic energy.
so K.E. of body = mv^2/2

Potential Energy - It is due to position of object.
example - Chemical energy from a bettery.
                Energy of a body placed at a height from earth surface.

Let an object of mass m is placed at h height from earth.
force F = mg ( here a = g gravitational acceleration )
work W = F.h
so W = mgh
This work is stored as potential energy.
P.E. of body = mgh