Define kinetic energy and potential energy. Write an expression for the kinetic energy of a body of mass m moving with a velocity v. Find the kinetic energy of a body of mass 40 kg moving with a velocity 15 m/s.

Kinetic energy: Energy possessed by a body by virtue of its motion is called its kinetic energy.

Mathematically, kinetic energy is expressed as, 

                       K.E  = $\frac{1}{2}m{v}^2$ 

where, 

m is the mass of the moving body,
v is the velocity of the body.

Potential energy: Energy possessed by a body by virtue of its position or shape is called its potential energy.

For a body of mass m lying at a height h above the ground level, gravitaional potential energy is given by, 

                         P.E = mgh 

Given,

Mass of the body, m = 40 kg
Velocity of the body, v = 15 m/s

So,  K. E. = 1 mv²  = 1 x 40 x (15)² = 4500 J.
                  2             2