A 10 kg ball is dropped from a height of 10 m. Find (a) the initial potential energy of the ball, (b) the kinetic energy just before it reaches the ground and (c) the speed just before it reaches the ground.

Explanation

Mass of the ball = 10 Kg , It is dropped from a height h = 10 m
Acceleration due to gravity g = 9.8 `m//sec^(2)`
a) The initial P.E. of the ball = mgh `10 times 9.8 times 10=980J`
b) We know that the energy is conserved in a freely falling object at anywhere in its journey.
`therefore` The K.E.just before it reaches the ground = 980 J
c) K.E. just before it reaches the ground = 980 J ,
Speed = v m/s
`1/2mv^(2)=980 rArr 1/2 times 10 times v^(2)=980 rArr v^(2)= 980/5 rArr y^(2)=196`
`therefore v=sqrt(196)=14 m//s.`