Momentum Demonstration

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Materials: basketball and tennis ball

 

What to do: Simply hold the tennis ball directly on top of the basketball while holding both in mid-air. Then drop them simultaneously to the floor. If the tennis ball was directly in the center top of the basketball, it will shoot up into the air, really high! The basketball will simply bounce a little, pretty much like normal. Be careful, because if the tennis ball is directly on the top, center of the basketball, it will shoot off at some angle, which still works, but be careful not to hit anyone (or yourself).

What's going on: What's going on here is that when you drop the basketball and tennis ball they both have momentum (a vector) pointing down, as they fall. The basketball hits the ground an instant before the tennis ball hits the top of the basketball. So when the basketball hits the ground, the ground acts to reverse the direction of momentum of the basketball so that it's toward the tennis ball. Then when the tennis ball hits the basketball, they collide, and since momentum has to be conserved, and the mass of the basketball is much greater than the tennis ball, so the velocity of the tennis ball will have to be dramatically faster, so it shoots up into the air.

This is also what happens in a supernova explosion. The outer layers of the star collapse into the center of the star, but once they get into the center, they have no where to go, so they bounce back. The basketball represents an inner layer, while the tennis ball is an outer layer, so when the inner layer bounces, it transfers its momentum to the outer layer, which shoots out into space at an extremely high velocity.