The word kinetic is derived from the Greek word “kinesis” meaning motion. When an object is moving, it possess a energy and such energy is called kinetic energy. The object includes very large things, like planets, and very small ones, like atoms. Heavier objects moves faster and have more kinetic energy. Kinetic energy may be best understood by examples that demonstrate how it is transformed to and from other forms of energy. 
Kinetic Energy Definition

Kinetic energy is one of many types of energy that exist. This is energy generated because something is moving — the faster it's going, the more kinetic energy it has. A person sitting has no kinetic energy, but a person running like a maniac has tremendous kinetic energy:
 The energy possessed by a body because of its motion, equal to one half the mass of the body times the square of its speed.


Kinetic Energy Definition

The amount of kinetic energy KE of an object in translational motion is equal to onehalf the product of its mass m and the square of its velocity v.

Kinetic energy is given as follows,
Kinetic energy = ½(mv2)
 The greater the mass and/or the speed of a moving object, the greater its Kinetic Energy.


Kinetic Energy Calculation
All moving objects have kinetic energy. The kinetic energy an object has depends on its:
The equation for calculating kinetic energy:
KE = ½ mv2
or
KE = ½ × m × v2
 KE = the kinetic energy in joules, J
 m = the mass in kilograms, kg
 v = the speed in metres per second, m/s


Example for kinetic energy calculation
A rocket of mass 1.5x104 kg accelerates at 220m/s2 for 29s from an initial speed of 5200m/s.
(a) How fast will be rocket be travelling after the 29s?
(b) How much Kinetic Energy has the rocket gained?
Solution:
Given:
t = time = 29s
a = acceleration = 220m/s2
v = final speed = ?
u = initial speed = 5200m/s


Formula
(a) a=(vu)/t
v – u = at
v = u + at
(b) KE = ½(mv2)


Calculation
(a)
v = u + at
v = 5200 + (220 x 29)
= 5200 + 6380
so
v = 11580m/s


(b) Now KE=½(mv2)
Initial Kinetic Energy =0.5 x (1.5x104) x (5200)2
=2.028 x 1011J
Final Kinetic Energy =0.5 x (1.5x104) x (11580)2
=1.006 x 1012J
Kinetic Energy gained = Final Kinetic Energy Initial Kinetic Energy
=1.006 x 1012J  2.028 x 1011J
=8.032 x 1011J



