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In the previous sections, we have discussed the basics of work and energy. In this section, we are concentrating on the energy contained by the moving object.
In our daily lives, we may come across the following questions,
  • How does a bullet pierce the target?
  • How does the wind drive the blades of a windmill?
In these cases, a bullet and the wind are in motion.
A moving object can do work. An object which is moving faster can do more work than the same object moving comparatively slow.
A moving bullet, blowing wind, a rotating wheel, a speeding stone can do work.
Objects in motion contain energy. We define this energy as kinetic energy.
A coconut is falling from the tree, a speeding car, a rolling stone, a flying aircraft, running water, blowing wind, a running athlete etc., possess kinetic energy.
In short,
kinetic energy is the energy contained by an object due to its motion. The kinetic energy of an object increases with its speed.
How much energy is contained by a moving body by its motion? By definition,
We say that,
The kinetic energy of a body moving with a certain velocity is equal to the work done on it to make it acquire that velocity.