Rubber Band Wheel

Relevant Resource questions :

Concepts demonstrated :

• First Law of Dynamics applied to rubber bands
• Thermal expansion of solids
• Adiabatic processes

• large rubber bands (long)
• mass carrier and masses
• retort stand
• thermocouple
• bunsen burner and matches or heat gun
• CCD camera

• Attach rubber band to the retort stand with a mass hanging from the end.

None.

Physics involved :

When the rubber band is stretched it gets colder (?).

When allowed to return to its normal size it will heat up (?).

When heated the rubber band will contract.

How to use the Demonstration :

• Measure the temperature of the rubber band when not extended, then allow the mass to drop, stretching the rubber band.
• Measure the new temperature of the rubber band and describe the situation as a adiabatic process (deltaQ = 0).
• Ask the students to predict what will happen to the temperature. Use Predict, Observe, Explain (POE) with a show of hands to indicate whether they think the termperature will increase/decrease/stay the same.
• The rubber band may also be heated using the bunsen.

• Gas escaping from a car tire.

• Hand out rubber bands to the students as they enter the lecture theatre and get them to perform the above experiment. The cheek on your face acts as a good temperature sensor.
  Ask the students to take the rubber band, expand it quickly and then place it against their cheek to feel any temperature change.
  NB it is difficult to determine the change in termperature for this experiment.
• Perhaps do the demonstration, ask POE and then get the students to repeat the experiment. Ask another POE based on their own experiment.
• A poster for Open Days would be good.

• The experiment may need smartening up.
• Develop a rubber band engine.