Physics behind a bouncing ball: Ball at surface has potential energy; as the ball falls through air the potential energy changes to kinetic energy.
Law of Conservation of Energy states that energy is neither gained nor lost, only transferred from one form to another. Potential energy is changed to kinetic energy when the ball starts to fall. Some energy is changed to heat energy and/or sound (thud) energy.
Newton's Third Law of Motion states that for every action there is an equal and opposite reaction. Ball pushes on the floor, floor pushes back on the ball. When the unhappy ball hits the floor the ball does not spring back from the floor, whereas the floor pushes back on the happy ball causing it to rebound.
The rubber balls are made from long chains of polymers stretching on impact. Balls that have a lot of bounce like the Happy Balls have tightly linked polymers, therefore most of the energy is transferred back to motion. Whereas the Sad Ball's molecular structure is more loosely arranged which results in its motion being converted to heat energy. If the Sad Ball's temperature is cooled, heated or warmed, the ball will bounce. Densities of the balls vary slightly, but essentially the Neoprene ball has a density close to that of water while the Norsorex ball is a little more dense.
"Sad Balls" have a low resilience, tend to absorb both kinetic energy of the bounce; and have a thud sound on impact. Norsorex is good for clothing, sound insulation, seals & gaskets, shock absorbers, body armor. "Happy Balls" are softer, bounces well, and have a high coefficient (good bounce). Neoprene is good for swimwear and wet suits (holds heat).
Happy and Sad Balls behave differently, because of their physical properties. They roll at different speeds, they emit sound waves at different decibels, and they bounce at different heights on different surfaces. When the same force is applied on them their compression is different. Since they have different densities, they sink in different solutions at variable rates.
How will each ball behave upon release and impact?
Where did the energy go?
Explain how this effect would be different if balls were heated for ten minutes, then dropped.
How did the energy compare after they hit the floor?
What principles were explored in this activity?
What properties of each ball could be measured?