Question

A ball falls to the ground as shown below :

Figure

(a) What is the kinetic energy of ball when it hits the ground?
(b) What is the potential energy of ball at B?
(c) Which law you have made use of in answering this question?

Answer 1

(a) Total energy of a free falling object remains conserved.
So,
Kinetic energy at the ground = Potential energy at the top$=\boxed{80\mathrm{J}}$
(b) Total energy of a free falling object remains conserved.
So,
Total energy at A = Total energy at B
So,
(K.E)_A + (P.E)_A = (K.E)_B + (P.E)_B
Thus
Total energy at A = (K.E)_B + (P.E)_B
Therefore,
(P.E)_B = (80 – 48) J $=\boxed{32\mathrm{J}}$
(c) Law of conservation of energy is used in answering these questions.