For an impressive demonstration of energy conservation and momentum;

4 rubber balls of different sizes, one on top of the other, arranged on a plastic axle.

The bottom rubber ball is firmly connected to the axle, while the next two rubber balls can move on the axle, but cannot leave it.

Only the top, smallest rubber ball can move completely on the axle.

Ball diameter: 48/37/24/21 mm (delivered with two small replacement balls)

If you drop the impulse cannon from a certain height onto a solid floor, after impact the top, small rubber ball flies upwards at a multiple of the final falling speed v0 and can reach enormous heights.

If you mark the maximum heights (hM) on a wall, you can work out a connection to different starting heights (hA).