Derive an expression for kinetic energy of an object

Derive an expression for kinetic energy of an object.
If the velocity of an object is doubled. What will be change in its kinetic energy?
Answer:
Suppose a body of mass m is moving with velocity v. It is brought to rest by applying a retarding force F. Suppose it traverses a distance s before coming to rest.
Kinetic energy of body, KE = Work done by retarding force to stop it.
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