Trampoline: springs give the energy back
The same ball falls onto the floor, a soft trampoline and a stiff one. On the floor it stops dead; on the trampolines it bounces up again.
Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
Falling, the ball gains energy of motion. The trampoline’s springs compress, store it and give it back, tossing the ball up. The floor gives nothing back.
How to run it
- Press “Run”: three identical balls fall from the same height.
- Compare how far the soft and stiff trampolines sag.
- Compare the rebound height with the drop height.
Questions to discuss
- Which trampoline sagged more, and why?
- Why doesn’t the ball rise higher than it dropped?
The science
While falling, potential energy m·g·h turns into kinetic energy, then into spring energy k·x²/2 as the springs compress, then back into the ball. Some is lost in the impact, to friction and in the damper, so the ball rises lower than it fell (here about half the drop height).
Try it at home
Stretch a handkerchief over a bowl with a rubber band and drop a paper ball on it — it bounces like on a trampoline.
What to change in the editor
- Make the ball heavier — how does the sag change?
- Use very soft springs (k = 100).