Answer to Question #171794 in Physics for Charles

Question

A bicycle pump has a stroke of 200mm and is being used to pump up a tyre that is at a pressure of 4 bar. If the pump is pushed slowly, what distance do I need to move the plunger for the air to be admitted to the tyre? What would the distance be if the pump were pushed quickly? Assume that the pump starts at an atmospheric pressure of 1 bar.

Answer 1

It is hard to answer numerically as we don't know the tire volume and pump cross-section. But we know that the air heats up if we move the stroke quickly and it temperature may not change if it is moved slowly. Also, we know that when the air is heated, its volume and pressure increases. Thus, we can conclude that if the pump is pushed slowly, the distance one needs to move the plunger would be greater compared to quick plunger push.