Question

An object of mass m = 50 g is released from rest from a height h = 150 m above the ground. Calculate the kinetic energy and the potential energy of the object at the height H = h/5.

Answer 1

The total energy of an object at the initial point

$$E=KE+PE=0+mgh$$ $$=0.05\times 9.8\times 150=73.5\:\rm J$$

At the height $H=h/5=30\:\rm m,$ the potential energy of an object

$$PE=mgH=0.05\times 9.8\times 30=14.7\:\rm J$$

The kinetic energy

$$KE=E-PE=73.5-14.7=58.8\:\rm J$$