Question

A ball of mass 0.2 kg is thrown vertically upwards with an initial velocity of 20 m/s. Calculate the maximum potential energy it gains as it goes up.

Answer 1

P.E.=mgh

P.E.=0.2x20x9.8

P.E.=39.2J

Answer 2

$s = ut + \frac{1}{2} a {t}^{2} \\ s = 20 \times 2 - \: \: \frac{1}{2} \times 10 \times 4 \\ s = 20 \: m$
$p \: energy \: = mgs \\ = \frac{2}{10} \times 10 \times 20 \\ = 40 \: \: joule$