This is a satisfyingly simple activity with surprising results. Take a tennis ball and place it on top of a basketball… then release both at the same time.
Instant ball launcher!
You’ll find the top ball rockets off skyward while the lower ball hit the floor flat (without bouncing much, if at all). Now why is that? It’s easier to explain than you think…
Remember momentum? Momentum can be defined as inertia in motion. Something must be moving to have momentum. Momentum is how hard it is to get something to stop or to change directions. A moving train has a whole lot of momentum. A moving ping pong ball does not. You can easily stop a ping pong ball, even at high speeds. It is difficult, however, to stop a train even at low speeds.
Mathematically, momentum is mass times velocity, or Momentum=mv.
One of the basic laws of the universe is the conservation of momentum. When objects smack into each other, the momentum that both objects have after the collision, is equal to the amount of momentum the objects had before the crash. Once the two balls hit the ground, all the larger ball’s momentum transferred to the smaller ball (plus the smaller ball had its own momentum, too!) and thus the smaller ball goes zooming to the sky.
- two balls, one significantly larger than the other