A boy throws a ball straight up with a speed of 21.5 m/s. The ball has a mass of 0.19 kg. How much gravitational potential energy will the ball have at the top of its flight?

The boy gives the ball some kinetic energy when he throws it, and

the ball swaps its kinetic energy for gravitational potential energy

until it runs out of KE.

The KE of the ball when it leaves the boy's hand is

(1/2) (mass) (speed) ²

= (0.095 kg) (21.5 m/s) ²

= (0.095 kg) (462.25 m²/s²)

= 43.914 joules (rounded)

The ball keeps rising until it has swapped all of those joules

for potential energy. Then it stops rising and begins to fall.