# Kinetic Energy | Physics

Energy is available on earth in different forms. These forms are like kinetic energy, potential energy, electrical energy, heat energy etc. We know that a moving object can do work. An object which is moving faster does more work than an object moving relatively slow. Moving bullet, blowing wind, rotating wheel, a speeding stone all these things can do work. Have you ever given a thought? how does moving bullet pierces the target or how does the wind move the blades of the windmill? All these happen because the objects in motion possess energy and we call such kind of energy as kinetic energy. Lets consider more examples from our real-life for kinetic energy: a falling coconut, a flying aircraft, a speeding car. In fact all moving object possesses kinetic energy. Kinetic energy is nothing but the energy possessed by a body by the virtue of its motion. How much energy is possessed by a moving body by virtue of its motion? By the definition, we can say that kinetic energy of a moving body with a certain velocity is equal to the work done on it to acquire that velocity. Let’s express kinetic energy in the form of an equation. Consider an object of mass m, moving with a uniform velocity u. Let it now be displaced through a distance s when a constant force f acts on it in the direction of its displacement. From the work done W is equal to F * s, the work done on the object will cause a change in its velocity. So the initial velocity is now changed into it. Final velocity that is u to v. Let a be the acceleration produced. In our previous section, we have studied three equations of motion. The relation connecting the initial velocity, final velocity of an object moving with a uniform acceleration a and the displacement s is v^2-u^2 is equal to 2as. This gives s=v^2-u^2/2a. We know that F is equal to mass * acceleration. So we can write work done by the force F as W is equal to ma*( v^2-u^2)/2a. where W is equal to 1/2m(v^2-u^2). If the object is starting from it’s stationary position i.e., the initial velocity u is equal to 0, then the work done W is equal to 1/2mv^2. Now it is clear that the work done is equal to change in the kinetic energy of an object if u is equal to 0. Then work done will be 1/2mv^2. Thus the kinetic energy possessed by an object of mass m and moving with uniform velocity v, kinetic energy Ek is equal to 1/2mv^2. Here in this lesson we have learned about kinetic energy which is defined as the energy possessed by an object by the virtue of its motion and also we have derived an equation for kinetic energy that is 1/2mv^2.