# Any prerequisites for the exercises for Feynman's lectures?

## Main Question or Discussion Point

Summary:: I am mostly just being confused on the exercises for the feynman lectures on physics.

So I've been reading feynman's lectures on physics, and I also attempted the problems on the "exercises for the feynman lectures on physics". However, I have gotten almost every single problem wrong, and with no step by step solution, I am left mostly confused. Can anyone help me with providing any tips or prerequisites for the types of problems in the exercise book? If possible, I would also like maybe other materials which provide similar problems or teach the materials which can be used to serve as a prerequisite for these exercises.

The book can be found at: https://www.amazon.ca/Exercises-Feynman-Lectures-Physics-Richard/dp/0465060714/ref=sr_1_1?keywords=exercises+for+feynman&qid=1576198674&sr=8-1
The textbook which accompanies these exercises can be found at: https://www.amazon.ca/Feynman-Lectures-Physics-boxed-set/dp/0465023827/ref=sr_1_2?keywords=exercises+for+feynman&qid=1576198688&sr=8-2

Simon Bridge
Homework Helper
I found an online list of the exercizes here: https://www.feynmanlectures.caltech.edu/info/exercises.html
Many of them have worked solutions.

I would normally have said that the prerequisite to do them would be "secondary school senior level physics and maths". OR just "having understood the lectures".

Getting all of them wrong suggests you have an understanding the lectures problem.

The main point of the series is not so much to learn the facts of phyiscs from them, but the thought process as Feynman does it. Discovering how physics is done.

Without seeing you attempt it, I don't think I can advise you .. except for each "wrong answer" go back to that section in the lecture notes and see if you can apply the notes better. They are pretty self contained.

One of the problems with just having a numerical answer is that you cannot tell if the reasoning or the arithmetic is faulty. This is the main use of worked examples.

You are right it is tricky to find worked examples ... maybe I'll give it a go, writing a study guide. Howveer, I'm sure someone else has already done it.

Example: ex 1: Atwoods machine.

Without reading the lectures, I'd try it this way: by conservation of energy...
Energy gained net gravitational PE lose is mgh (loss in Mgh is balanced by the gain on the other side), this is gained as kinetic energy of all of the the masses.

So $mgh = \frac{1}{2}(2M+m)v^2$ ... as all the masses are travelling the same speed v, I just added up the kinetic energy terms for each mass... there are two of mass M and one of m.

After the unbalanced mass is gone ... the machine keeps going at constant speed v.

Seems to match the solution provided.

How does that compare with your reasoning?

Ah, so attempting the problem myself I used more of an algebraic approach, so I see your point regarding utilizing Feynman's thinking. However, I would also like to know if there are any recommended physics textbooks that I can read to get to the required level for this(I ask this because I am currently in the eighth grade, so all most my learning regarding this comes from online resources and books). Thanks, nevertheless, for taking the time to write a reply.

Simon Bridge
Homework Helper
I'm in NZ. So you are 12-13? You are doing well then.
The worked examples in the link I gave you will be a bit offhand in showing reasoning because the author is writing for a college level audience.

Your High School's physics text book (or of a High School near you) will probably be the best place to start.
The main reason being you will find people in meat-space near you who can help guide you with it.
Maybe look for a study guide for AP phyiscs.

I'm quite a ways removed from text books ... I tended to write my own. Offof Amazon, maybe
https://www.amazon.com/dp/B000XXF9V4/?tag=pfamazon01-20
https://www.amazon.com/dp/0809058405/?tag=pfamazon01-20

The first is to help with exercises you have to think your way through and utilize understanding of the concepts involved. The second contains a quick and very dirty intro to probability and statistics, in analysis. Both tyhe things that usually give students problems.

Have you seen:
https://www.amazon.com/dp/0345409469/?tag=pfamazon01-20

Also good for meta-reasoning.

You can see that I am primarily concerned with how you reason. That looks like your main hurdle, just off these few comments.

I would not normally recommend the Feynman Lectures as a way to self-study physics, however I do usually recommend finding a text that is beyond you and then working out where it loses you as a way to figure what to google. Good luck.

Note: the only algebra in my worked example is at the end ... divide both sides by mh to get an expression for g in terms of all the rest. That's it. The expression is just the "conservation of energy" reasoning translated into maths (in physics, maths is a language.)

Ok, thanks

anorlunda
Mentor
Ah, so attempting the problem myself I used more of an algebraic approach, so I see your point regarding utilizing Feynman's thinking. However, I would also like to know if there are any recommended physics textbooks that I can read to get to the required level for this(I ask this because I am currently in the eighth grade, so all most my learning regarding this comes from online resources and books).
I agree. You are doing well indeed.

One thing we all need to learn does not come directly from the books -- problem solving skills.
We get those skills by doing homework and solving problems. If you're having trouble, it may be that you are attempting difficult problems without enough practice with easy and medium problems. You're smart. If that is the cause of the trouble, what should you do about it?

PeroK
Homework Helper
Gold Member
Ok, thanks
Before you try a problem, do you think you understand the material? Why aren't you simply stuck on a problem, rather than getting it wrong?

I agree with the others that you are trying high level material. But, if you are doing problems thinking everything is fine, then find your solution is wrong that might be a worry.

It's definitely a good idea to post something in the homework forum on here.

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You might benefit from the book Feynman's Tips on Physics, a problem-solving supplement to The Feynman Lectures on Physics, which includes three lectures on problem-solving Feynman offered his students just before their first final exam. In them Feynman works out solutions to a bunch of problems, and also discusses problem-solving in physics more abstractly. In addition, the book includes a chapter on 'dynamical systems' with an emphasis on inertial guidance, plus essays/interviews with the original authors of FLP and the FLP exercises.

Before you try a problem, do you think you understand the material? Why aren't you simply stuck on a problem, rather than getting it wrong?

I agree with the others that you are trying high level material. But, if you are doing problems thinking everything is fine, then find your solution is wrong that might be a worry.

It's definitely a good idea to post something in the homework forum on here.
Since the material is currently above my level, would you recommend me putting the lectures aside, before attempting them at another time? Or instead to continue try to use the lectures and exercises but also utilize other materials alongside the lectures?

PeroK
Homework Helper
Gold Member
Since the material is currently above my level, would you recommend me putting the lectures aside, before attempting them at another time? Or instead to continue try to use the lectures and exercises but also utilize other materials alongside the lectures?
I'd say it's important to understand what you are studying. There's no point if it really is beyond you. You have to build up to that level of physics.

You have to judge for yourself. It's hard to know without seeing what you have learned and where you are struggling.

jtbell
Mentor
I suggest you use the Feynman lectures alongside one of the standard calculus-based introductory physics textbooks, e.g. Halliday/Resnick/Walker Fundamentals of Physics. I’ve always thought of the Feynman lectures as best used as a supplement to the standard textbooks. Try it both ways, with the textbook as primary and with Feynman as primary, and see which which works better for you.

ZapperZ
Staff Emeritus
Summary:: I am mostly just being confused on the exercises for the feynman lectures on physics.

So I've been reading feynman's lectures on physics, and I also attempted the problems on the "exercises for the feynman lectures on physics". However, I have gotten almost every single problem wrong, and with no step by step solution, I am left mostly confused. Can anyone help me with providing any tips or prerequisites for the types of problems in the exercise book? If possible, I would also like maybe other materials which provide similar problems or teach the materials which can be used to serve as a prerequisite for these exercises.

The book can be found at: https://www.amazon.ca/Exercises-Feynman-Lectures-Physics-Richard/dp/0465060714/ref=sr_1_1?keywords=exercises+for+feynman&qid=1576198674&sr=8-1
The textbook which accompanies these exercises can be found at: https://www.amazon.ca/Feynman-Lectures-Physics-boxed-set/dp/0465023827/ref=sr_1_2?keywords=exercises+for+feynman&qid=1576198688&sr=8-2
Unfortunately, Feynman text is not the best book to start with pedagogically. It is why it is not a very common text being used in a General Physics course. It is a good text to refer to once you have a more solid foundation of physics.

If you wish to study first-year physics and have calculus background, then many of the General Physics text (Knight, Halliday/Resnick, etc.. etc... ) may be the better options. Then go back to Feynman once you have an understanding of the basics.

Zz.