Question

A ball of mass 8kg falls from a height of 100m . Neglecting air resistance, calculate its total energy after falling a distance of 40m

Answer 1

The total energy of a ball

$$E=E_k+E_p=const$$

$$E=E_{k1}+E_{p1}=0+mgh_1\\ =8*9.8*100=7840\:\rm J$$