Question

A 5 kg ball dropped from rest at a height of 10 meters and rebounds from the floor with a speed of 12 m/s. How much energy is lost as a result of the bounce?

Answer 1

The initial energy of the ball is his potential energy:

E1 = m·g·h = 5[kg]·9.8[m/s²]·10[m] = 490[J].

The final energy of the ball is his kinetic energy:

E2 = m·V²/2 = 5[kg]·(12[m/s])²/2 = 360[J].

The difference is

E = E1 - E2 = 490[J] - 360[J] = 130[J].

So, the ball lost 130 joules.