# Feynman Lectures: The Random Walk Explained

• luuurey
In summary, the conversation discusses difficulties understanding a chapter in the Feynman lectures on physics, specifically the concept of random walk and its application to objects in a force and resistance environment. The speaker also expresses confusion over the equations presented and asks for assistance. The other person suggests reading the lectures alongside a contemporary text and approaching the concepts from a different perspective. They also offer suggestions for understanding the equations by considering their meaning and purpose.

#### luuurey

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.

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?

## 1. What is a random walk in physics?

A random walk is a concept in physics that describes the movement of a particle or system that is randomly scattered in space. It is a mathematical model that can be used to understand and predict the behavior of various physical phenomena, such as the movement of molecules in a gas or the price changes in financial markets.

## 2. Who is Richard Feynman and why are his lectures important?

Richard Feynman was a renowned American physicist who made significant contributions to the fields of quantum mechanics and particle physics. His lectures, known as the Feynman Lectures on Physics, are considered a classic in the field and are widely used as a reference for students and researchers. They are known for their clear explanations and intuitive approach to complex concepts.

## 3. How does the random walk model apply to real-world situations?

The random walk model can be applied to various real-world situations, such as the movement of molecules in a gas, the diffusion of chemicals in a liquid, the trajectory of a particle in a magnetic field, and the spread of diseases in a population. It can also be used to analyze stock market trends and predict future prices.

## 4. What are some limitations of the random walk model?

While the random walk model is useful in many applications, it has some limitations. For example, it assumes that the steps taken by the particle are completely random, which may not always be the case in real-world situations. In addition, it does not take into account external factors that may affect the movement of the particle, such as gravity or air resistance.

## 5. How can the random walk model be improved?

There are several ways to improve the random walk model, such as incorporating more realistic assumptions, such as non-random steps or external influences. Another approach is to use more advanced mathematical techniques, such as the Monte Carlo method, to simulate the movement of particles in a more accurate manner. Additionally, incorporating data from real-world experiments can also help to improve the accuracy of the model.