Feynman Lectures: The Random Walk Explained

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SUMMARY

The forum discussion centers on the complexities of understanding the chapter "The Random Walk" from the Feynman Lectures on Physics, specifically around equations 41.18 and 41.19. The user expresses confusion regarding the implications of the average values \left\langle x v_x \right\rangle and \left\langle x F_x \right\rangle, particularly in relation to particle behavior in a gas and the effects of resistance. A suggestion is made to read the Feynman Lectures alongside more contemporary texts for better comprehension, as they serve as a refresher for those already familiar with basic physics concepts.

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Students of physics, educators seeking to clarify complex concepts, and anyone interested in the mathematical foundations of random walks and their implications in physical systems.

luuurey
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There is a chapter in Feynman Lectures on Physics called The Random Walk(41-4). I understand everything till the paragraph right after equation 41.18. I have no idea what he is trying to say. There is an equation 41.19, which is diff. eq. for object that is forced and is in a environment that causes resistance... that is not eq. of particle in a gas. Than he is saying that average of \left\langle x v_x \right\rangle does not change because it doesn't remember where it was before.. I don't understand that formulation. I am also not sure why \left\langle x F_x \right\rangle = 0.

Could someone help me please ?
Thank you very much.
 
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The Feynman lectures were not very effective when Feynman was giving them - they tend to the over-clever - I don't think they are that great now. You are best advised to read them alongside or after a more contemporary text... they tend to work best as a refresher course for people who have already done the basic physics by another method.

However, your questions can be approached by considering the converse. i.e. what does it mean for <xF> not zero, and <xv> not constant? What do xv and xF measure?
 

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