Kinetic Energy: Energy possessed by a body by virtue of its motion is called kinetic energy. Any moving body has kinetic energy. Kinetic energy is the energy an object has because of its motion.
When a nail is struck by a hammer strongly on a wall the nail enters inside the wall overcoming the resistance of the wall. The hammer can do this work because of its motion i.e., due to the kinetic energy of the hammer the nail can overcome the resistance of the wall.
You have seen sailing boats in the river. Kinetic energy of the current in the river drives away the boat. When wind flows strongly, then the boat can move fast if sail is hoisted. Using the kinetic energy of wind the boat can move fast by hoisting the sail.
While coming down on the plane from hill current in the river flows strongly. Due to strong kinetic energy of the current large stones can be driven by the river.
Again, competitors while making high jump and long jump do not jump from rest, but do jump after running a certain distance. As a result, they can go a long distance by jump.
From all the above events it is observed that while stopping a moving body by applying external force, the total amount of work done by the body before coming to rest is the measure of kinetic energy of the body.
Unit: Unit of kinetic energy and work is the same. That means, unit of kinetic energy is joule ‘J’.
[Ek] = [½ mv2]
= [M] [LT-1]2 = [ML2T-1]