Spring cannon: from spring energy to range
Three identical cannons with springs of different stiffness fire at 45°. The stiffer the spring, the farther the ball goes: twice as stiff, roughly twice as far.
Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
A compressed spring stores energy and passes it to the ball at the shot. The stiffer the spring, the more energy for the same compression and the faster the ball leaves.
How to run it
- Press “Run”: after a second the latches release and the cannons fire.
- Compare the ranges: the left cannon has k = 300, the middle 200, the right 100.
- Select the right cannon’s spring and set k = 400.
Questions to discuss
- How many times farther does the ball go when the spring is twice as stiff?
- What changes if you compress the spring more?
The science
The energy of a compressed spring E = k·x²/2 turns into kinetic energy m·v²/2. The range at 45° is R = v²/g, so it is proportional to the stiffness k (for the same compression x). Compressing the spring twice as much quadruples the energy.
Try it at home
Take a click-pen apart, compress its spring and let go: it hops. The more you compress it, the more energy it stores.
What to change in the editor
- Change the cannon angle — which angle gives the farthest shot?
- Use a heavier ball (m = 2).