A demonstration from my days as a science teacher:

Hook a few rubber bands together in a chain.
Attach one end to a support and hang enough weight on it so that it
reaches its maximum normal extension.
Quickly pass the flame from a propane torch along the chain of rubber bands.
The weight is typically lifted about 10% of the length of the rubber bands.

There is also a more elaborate version where the spokes of a bicycle
wheel are replaced by rubber bands.
A heat lamp shining on the rubber bands on one side of the wheel shifts
the center of gravity and makes the wheel rotate continuously.

Larry A.

Jim Felder wrote:

>
> And I don't know about rubber expanding when cold. Every time I need to
> force a resistant hose over a fitting I end up submersing the tubing
> end in boiling water!
>
> Jim
>
>
> On Nov 20, 2005, at 5:00 AM, Daniel L. Katz wrote:
>
>> wait a minute!! when it's cold the whole van shrinks, but the plastic
>> pipe
>> shrinks less in proportion because plastic has a smaller coefficient of
>> expansion than metal, and rubber, of course, expands when cold.
>>
>> dan
>>