Define potential energy. Derive an expression for the gravitational potential energy of object of mass 'm' at a height 'h' above the earth's surface. A ball of mass 0.25 kg is moving with a velocity of 25 m/s. Calculate its kinetic energy.

Dear Student ,

Potential Energy:

The energy possessed by a body by virtue of its position relative to others, stresses within itself, electric charge, and other factors.
 

Any object on the earth is pulled towards the centre of the earth with a force equal to the weight of the object. An object of mass ‘m’ will be pulled towards the earth’s centre by a force equal to ‘mg’

So, to lift the object without any acceleration a force equal to its weight must be applied in the opposite direction (away from the centre of the earth).

We have, Force = mg, to lift the object. Suppose, h is the height attained by the object due to this force. The work done by this force is stored as gravitational potential energy of the object.

Therefore, potential energy = work done = mgh

So here the kinetic energy of the ball of mass 0.25 kg and velocity 25 m/s is =Ek = 1/2mv‚Äč2 = 78.125 J
Regards

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Q 16.

Given : Mass (m) = 0.25 kg
             Velocity (v) = 25 m/s

Find : Kinetic energy of  a moving ball ?


Soln : 
Kinetic energy = 1/2​mv2
                        =1/2×0.25×252
                        =1/2×0.25×625
                        =1/2×156.25
                        =78.125J
The kinetic energy of the moving ball is 78.125J.
 
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