A 10kg ball is thrown into the air. it is going 3m/s when thrown. How much potential energy will it have at the top?

According to law of conservation of energy;

Potential energy at the top = kinetic energy at the bottom

as the ball travels upwards, its kinetic energy is converted into potential energy, such that at its maximum height, all kinetic energy will be converted into potential energy.

Potential energy (PE) = mass (m) * gravitational acceleration (a) * height (h)

where m = 10 kg, a = 9.8 m/s² and h = ?

Kinetic energy (KE) = 0.5*mass (m) * velocity (v) ²

where m=10 kg, and v=3 m/s

KE=0.5*10*9=45 J

since KE = PE; PE = 45 J