University of Wisconsin Stout | Wisconsin's Polytechnic University

The Bicycle Pump

A student pumping up a bike tire notices that as they pump with vigor that the bicycle valve and pump itself appears to be warm. The student points this out to some friends and they discuss the possibilities.

• A. One student says that it is simply friction of the pump handle and action that heats the air and the pump.
• B. A second students says it's a thermodynamic effect, that the work being done goes both into compressing and also heating the air.
• C. A third student says it's really the interaction of the compressed air and the valve. As the compressed air in the pump tries to rush into the small throat of the valve, many air molecule collisions take place heating the air and the valve.
• D. Where do you get these questions?

Answer