A quick bicycle experiment
If you ask a dozen physicists this question you won't get
agreement. So try it, it'll only take a couple of minutes.
- Turn a bicycle upside down so that it is resting on the handlebars
and the saddle.
- Wind the pedals round by hand and get the back wheel spinning.
- If the cycle starts bouncing up and down on the saddle springs
- Spinning faster to break the resonance
- Let the wheel come naturally to rest. Add a bit of plasticine or
putty to the TOP rim. After a couple of goes the wheel should be balanced.
- Jam on the brakes.
Are the saddle springs...
- Compressed (Bicycle pushes down)
- Relaxed (Bicycle tries to take off)
- Not affected
- Something else happens
The fun of this experiment is that once you know, you can ask a physicist and
get an answer along the lines of a dressed-up guess: "I think it should
...". See how much money you can wager on it. Be subtle