Feynman lectures on physics: random walk

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Discussion Overview

The discussion revolves around understanding specific formulas (6.11 and 6.12) from volume 1 of the Feynman Lectures on Physics, particularly in the context of a random walk scenario involving coin tossing. Participants seek clarification on the mathematical expressions and their implications for energy changes in a system.

Discussion Character

  • Exploratory
  • Technical explanation
  • Homework-related

Main Points Raised

  • One participant expresses confusion about the clarity of the text surrounding formulas (6.11) and (6.12) and requests a simpler explanation.
  • Another participant suggests providing links to the formulas for better context and encourages specificity in questions.
  • A participant explains the random walk concept using a coin toss game, detailing how the distance from the starting point is calculated based on the number of heads and tails.
  • There is a reiteration of the explanation regarding formulas (6.11) and (6.12), emphasizing their role in understanding changes in internal energy related to volume, pressure, and heat.
  • Some participants note the importance of links for easier access to the material being discussed.
  • A later reply questions the relevance of the explanation about internal energy, indicating a lack of clarity or agreement on the topic.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the interpretation of formulas (6.11) and (6.12), with some focusing on the random walk aspect while others discuss internal energy changes. The discussion remains unresolved regarding the clarity and application of these formulas.

Contextual Notes

There are limitations in the discussion, including missing assumptions about the context of the formulas and the varying interpretations of their significance. The reliance on specific definitions and the scope of the discussion may also affect understanding.

YanaFFF
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TL;DR
Explain please
I do not understand the formulas (6.11) and (6.12) in volume 1 of the Feynman lectures on physics, the entire paragraph between equations (6.10) and (6.12) is generally not very clear. Please explain (preferably in simple language, I'm 13). Thanks!
 
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It would help if you provided links to those formulas for those of us a don’t have Feynman lectures on our shelves. It would also help if you were more specific about what exactly you don’t understand.
 
As kuruman says, it's helpful to provide links to things you want to ask questions about. We're helping out just for fun, and you're more likely to get help if we only have to click on one link rather than hunt through search engines for references. It isn't always possible to provide links, of course, but the Feynman Lectures are all online on CalTech's website - this is chapter 6.

He's proposing a game: toss a coin and if you get heads take a step to the left, if you get tails take a step to the right. If you keep repeating this game, how far will you be from your starting point? The answer is the difference between the number of heads you've got so far and the number of tails you've got so far. This is ##D##. He does algebra to get different expressions for ##D## in terms of the total number of tosses and the number of heads. This is useful because ##N## is not a random number and nor is 2, so the randomness of ##D## is dictated by the randomness of ##N_H##, and he already did the maths for that.

6.11 is just a rearrangement of ##D=2N_H-N##, stated in the paragraph above. 6.12 expects you to use 6.11 to see that the left hand side is the same as half the rms value of ##D## and then 6.10 to get the right hand side.

If that doesn't make sense, say which bits you don't follow and we'll see what we can do.
 
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Ibix said:
As kuruman says, it's helpful to provide links to things you want to ask questions about. We're helping out just for fun, and you're more likely to get help if we only have to click on one link rather than hunt through search engines for references. It isn't always possible to provide links, of course, but the Feynman Lectures are all online on CalTech's website - this is chapter 6.

He's proposing a game: toss a coin and if you get heads take a step to the left, if you get tails take a step to the right. If you keep repeating this game, how far will you be from your starting point? The answer is the difference between the number of heads you've got so far and the number of tails you've got so far. This is ##D##. He does algebra to get different expressions for ##D## in terms of the total number of tosses and the number of heads. This is useful because ##N## is not a random number and nor is 2, so the randomness of ##D## is dictated by the randomness of ##N_H##, and he already did the maths for that.

6.11 is just a rearrangement of ##D=2N_H-N##, stated in the paragraph above. 6.12 expects you to use 6.11 to see that the left hand side is the same as half the rms value of ##D## and then 6.10 to get the right hand side.

If that doesn't make sense, say which bits you don't follow and we'll see what we can do.
Thank you very much! That's exactly what I wanted to hear.
 
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Ibix said:
We're helping out just for fun, and you're more likely to get help if we only have to click on one link rather than hunt through search engines for references.
Especially when one is using a smartphone to search.
 
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Formulas (6.11) and (6.12) in Feynman's lectures on physics explain how the energy of a system changes if it is divided into two parts. This is called a change in the internal energy of the system. Formula (6.11) says that the change in internal energy depends on the change in the volume of the system and pressure. And formula (6.12) shows that the change in internal energy also depends on the heat received or lost by the system. Thus, these formulas help to understand how the energy of a system changes under different conditions.
 
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AlexisBlackwell said:
Formulas (6.11) and (6.12) in Feynman's lectures on physics explain how the energy of a system changes if it is divided into two parts. This is called a change in the internal energy of the system. Formula (6.11) says that the change in internal energy depends on the change in the volume of the system and pressure. And formula (6.12) shows that the change in internal energy also depends on the heat received or lost by the system. Thus, these formulas help to understand how the energy of a system changes under different conditions.
Say what?
 
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