Question

The stone of mass 2 kg is allowed to fall freely from the top of a cliff of
height 60 m. What is the kinetic energy of the stone when it just reaches
the ground? [take g = 10 m/s 2 ]

Answer 1

When ball is at rest it will only have Potential Energy that is,

P.E=mgh

m= 2 kg;h=5 m

P.E=2×10×5=100J

This is the total energy as K.E is zero when the ball is at maximum height that is when it is at 5 m. Hence when the ball reaches the ground P.E becomes zero because of zero height.At this point,the total energy is equal to the K.E that is K.E=100J.

Answer 2

Answer:

Initial potential energy =Mgh

2x60x10