Average relative velocity in calculating mean free path

AI Thread Summary
The discussion centers on the use of root mean square (RMS) relative velocity in calculating the mean free path. Participants debate whether using mean-relative speed instead of RMS would yield different results, with one noting that mean-relative velocity would be zero due to its vector nature. The conversation emphasizes the need to adjust derivations if mean-relative speed is used, suggesting that RMS speed is preferred for its mathematical properties. Ultimately, the discussion encourages practical experimentation with calculations to understand the implications of using different speed measures. Understanding the differences between these approaches is crucial for accurately applying concepts like mean free path in physics.
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Try it and see what happens when you use the mean-relative-velocity. ;)
 
Thanks Simon,

I'm not really following. The mean-relative-velocity would be 0 since velocity is a vector. I think I meant to say mean-relative-speed. I would expect the mean-relative-speed to be less than the rms-relative-speed but that's about it.

Thanks
 
Ri-ight - so, look through your notes about mean free path, where it is applied (say: brownian motion) and use your idea of the mean-speed instead of the rms speed. (You'll have to adjust the derivation to account for the difference.) See what you get.

I could go and just describe in words why the rms speed is preferred etc etc ... but that's a lot of typing when I can just make you do the math. You asked the question: are you prepared to find the answer?
 

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