The shock absorber: keeping the body from bouncing
Two identical cars drive over bumps: the top one has only a spring, the bottom one a spring and a shock absorber. The top body bounces for a long time, the bottom one settles quickly.
Press “Run”. Bodies move by the laws of physics: gravity, friction, elasticity.
What the experiment shows
A spring softens the blow but on its own sets the body bouncing again and again. A shock absorber damps the motion, turning its energy into heat.
How to run it
- Press “Run”: both cars cross the first bump.
- Watch the body after the bump: how many times does it bounce up and down?
- Select the top car’s spring and set damping d = 250.
Questions to discuss
- Why is a car without shock absorbers dangerous on a bumpy road?
- What happens if the damper is too strong?
The science
A body on a spring is an oscillator with frequency √(k/m). A damper adds a force proportional to speed, F = −d·v, which removes energy from the oscillation. Too little damping leaves the bouncing; too much makes the suspension hard; the best is near critical damping d = 2√(k·m).
Try it at home
Press down on a parked car’s hood and let go: a healthy car bounces once, one with worn shock absorbers bounces several times.
What to change in the editor
- Increase the spring stiffness to 6000.
- Increase the speed of the cars.