A body of mass 25 kg is raised to the top of a building 10 m high and then dropped freely under gravity (g = 10 m/s2):
(a) Calculate the work done in raising the body to the top of the building.
(b) What is the value of the gravitational potential energy at the top of the building?
(c) By what factor will the gravitational potential energy of the same body increase if it is raised to the top of a multistorey building 30 m high?
(d) When will the kinetic energy of the body be maximum?
Given that,
Mass of the body, m = 25 kg
Height to which the object is rasied up, h = 10 m
Acceleration due to gravity, g = 10 m/s2
(a) Work done = mgh
= 25 x 10 x 10 J
= 2500 J.
(b) Gravitational P.E. = work done = 2500 J
(c) Gravitational P.E. at a height of 30 m is,
P.E= 25 x 30 x 10 J = 7500 J
(d) K.E. of the body will be maximum just before the body strikes the ground.
