Question

What is the potential energy of a 1-kilogram ball is thrown into the air with an initial velocity of 30m/sec?

Answer 1

mass=1kg
g=10m/s^2 (assuming)
u=30m/s
height(h)=u^2/2g
=900/20=45m
P.E.=mgh
=1×10×45=450 joules

Answer 2

the ball thrown from height=0
potental energy(PE) =0
kinetic energy(KE) = 0.5mv^2 = 0.5(1)(30^2) = 450

at the highest point the ball does not moved, v=0
potential energy at its maximum
kinetic energy = 0

Energy is conserved then
total energy before = after
PE1 + KE1 = PE2 + KE2
0 + 450 = PE2 + 0

conservation of energy is fun fact