Question

A man carries a 45kg rock halfway up a hill of height 650m. What is the potential energy of the rock? If the rock falls to the bottom of the hill, what will it's new potential energy?

Answer 1

Given :

Mass of the rock carried by man = 45 kg

Height of the hill = 650 m

The man carries the rock halfway upto the hill .

To Find :

What is the potential energy of the rock and if the rock falls to the bottom of the hill then what will be it's new potential energy?

Solution :

Let us consider the potential energy of the rock at the bottom the hill to be zero .

∴We know that potential energy is given as :

P.E. = mgh

Here m is mass of the body , g is acceleration due to gravity and h is height .

So, potential energy at the half of the hill :

= $45 \times 10 \times \frac{650}{2}$

= 146250 J

Hence , the potential energy of the rock at halfway to the hill is 146250 J and when it fall to the bottom its new potential energy will be 0 .