September 20, 2021, 10:16:23 AM
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Topic: Why does a bike pump get hot when you use it? and other stupid question.  (Read 17533 times)

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Aleck

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No, I did not come up with the question, but unfortunately I am the one who has to find the answer. So, as you can imagen, its probably not something too hard to explain if you know the answer, but its not exactly a question hundreds are racing to publish the answer to either. So if anyone could please help with answering one of the following...

Why do bike pumps get hot when you use them? (and its nothing to do with friction)
What happens to water and staem at 100 degress celcius? and what is the difference? (the answer has to be more than it boils)

Thankyou already for taking the time to completely read my post, now... any answers while I continue to search and grow more frustrated?

Offline Donaldson Tan

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Re:Why does a bike pump get hot when you use it? and other stupid question.
« Reply #1 on: February 16, 2005, 12:03:42 PM »
when you pump air inside a bicycle, you perform mechanical work on the air. hence, the internal energy of air increases. this results in increased temperature.

water boils at 1atm, 100C. water and steam coexist at this temperature and pressure. however, one needs to supply energy to break the intermolecular bonds within the water molecules in liquid state in order for it to become steam.
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Offline jdurg

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Re:Why does a bike pump get hot when you use it? and other stupid question.
« Reply #2 on: February 16, 2005, 03:44:59 PM »
When a gas is compressed its temperature increases.  When the compression is released, the temperature drops.  This is the primary basis on how liquid nitrogen is formed.  They take air and put it through numerous compression/decompression cycles.  Each time they cycle it, the temperature of the air drops until it becomes a liquid.  With the bicycle pump, you are compressing the air as you're pumping it into the tire so the pump is exposed to that increase in temperature.  The air doesn't get decompressed in the pump, however, so it doesn't experience the cooling effect.  (Since when you draw the pump back you're just taking in more air from the outside and not decompressing the air that was in there).  So over time, this increased temperature causes the pump to become hotter.  

The expansion/contraction of a gas under pressure is an adiabatic process.  That means that as the volume changes, the temperature changes as well.  In the bike pump the pressure of the gas is increasing so the temperature is increasing as well.  You can feel that temperature increase in the pump, but if you were to measure the temperature of the tire you would see that it was a bit lower since the expanding gas was cooling in temperature.
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Aleck

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Re:Why does a bike pump get hot when you use it? and other stupid question.
« Reply #3 on: February 17, 2005, 04:16:04 AM »
Wow... you are truely beautiful people! Thanks a whole bunch for that. I really had a hard time finding anything even touching on the subject. Thanks again.

Offline BurntFinger

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Holy flippin' necrobump!   

9yr+ old thread helping relieve the itch in my brain about how the hell that bicycle pump got so damn hot (huge blister on the side of my finger from it)


If you ever read this jdurg;  Thank you for the perfect explanation, fit even for an injured layman to grasp. 


I'll check back in 2023 and see how the threads doing ;D

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