Kinetic Energy

A moving cricket ball can knock down the stumps. The cricket ball has energy because of its motion. When a stone is thrown with a great force, this fast moving stone can hit a window pane and break it. The stone has energy to do work on the window pane because of its motion. Thus, the energy possessed by a body due to its motion , is called Kinetic Energy.

                                                                                                                                            Kinetic Energy (K.E.) of a body having mass m, and velocity v, is equal to 1/2 mv 2.

                                                                  
                            i.e. K.E. = 1/2 mv 2

If  'm' is in kg, and 'v' is in m/s, then K.E. is in Joule (J).

1. Since the kinetic energy of a body is directly proportional to its mass, therefore, if the mass of a body is doubled, its kinetic energy also gets doubled and if the mass of body is halved, its kinetic energy also gets halved.
2. Since the kinetic energy of a body is directly proportional to the square of its velocity, therefore, if the velocity of a body is doubled, its kinetic energy becomes four times, and if the velocity of a body is halved, the kinetic energy becomes one-fourth.

Some examples of Kinetic Energy from our day to day life are:

1. The kinetic energy of running water is used to run the water mills.
2. The kinetic energy of the hammer is used to drive a nail in wood.
3. A bullet fired from a rifle can penetrate into a target because of its kinetic energy.