Stacked Three Ball Drop STEM Challenge

A stacked ball drop demonstration is a brilliant way to demonstrate momentum transfer between objects. The compression of the bigger two balls bounces the smallest ball much higher than it would normally bounce.

girl holding 3 different sized balls for a 3 ball stacked drop

You'll need

A basketball

A tennis ball or small basketball/football

Table tennis ball or golf ball

Stacked Three Ball Drop Instructions

Hold your arms outstretched and drop the smallest ball. Watch how high it bounces.

Place the tennis ball on top of the basketball, drop them both, and watch what happens.

Stack the three balls on top of each other, with the smallest at the top. Try to hold them straight. Let them drop and watch what happens.

What's happening?

When held in the air each ball has an amount of potential energy. When the ball hits the ground, it compresses.

When the basketball hits the ground, it compresses slightly, storing potential energy. When the ball starts to leave the ground, the energy is released to the smaller tennis ball, which allows it to bounce higher than it would without the basketball. The basketball transfers its higher momentum ( from its greater mass ) to the smaller ball.

You'll notice the bigger balls bounce less than expected as they have lost energy to the smaller balls.