# Grad school is crushing my soul.

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The book we're using for mechanics is "Theoretical Mechanics of Particles and Continua" by Fetter and Walecka. I've never had as much trouble understanding physics as I am now. I am absolutely confounded when it comes to Lagrange multipliers, Euler angles (and other rigid body stuff) and Hamiltonian dynamics. Our prof is generally pretty unhelpful. Does anyone have a book that explains this stuff clearly and succinctly? I've heard Goldstein or Landau are pretty good. Confirm/deny?

Does this whole grad school thing get easier to manage after 1st year? I'm only taking 4 classes and I feel completely overwhelmed (compare to 6 as undergrad). Ugh.

Pengwuino
Gold Member
Goldstein is pretty good, haven't really looked at Landau yet.

Grad classes are nothing like undergrad classes and 4 is pretty much the most i ever hear anyone expected to take. Grad school sucks. Undergrad life was "I wonder if I have time for homework after I play my video games". Grad life is "I wonder if I have time to sleep after I do my homework".

Fredrik
Staff Emeritus
Gold Member
I passionately hated Goldstein (2nd edition, haven't seen the 3rd). The next year that class was given, they used Scheck instead. It looked really nice. Not sure how well it covers the specific topics you need though. You can probably find out for yourself. Another book worth taking a look at is Arnold. Unfortunately I've only had time to read a very small part of it

Sounds about right then. If I get 6 hours of sleep I consider myself lucky.

Thanks Fred, I'll hit the library up tomorrow and look for those :)

Goldstein is pretty good, haven't really looked at Landau yet.

Grad classes are nothing like undergrad classes and 4 is pretty much the most i ever hear anyone expected to take. Grad school sucks. Undergrad life was "I wonder if I have time for homework after I play my video games". Grad life is "I wonder if I have time to sleep after I do my homework".

I suppose that's the same for math grad school?

lisab
Staff Emeritus
Gold Member
Sounds about right then. If I get 6 hours of sleep I consider myself lucky.

Don't short your self too much on the sleep. I know you know this, and I knew it too when I was in school. But I still chose to study rather than sleep, and I really regretted it. It severely limits your creativity and speed of learning.

D H
Staff Emeritus
Ditto on Goldstein being pretty good.

Your first year of grad school is essentially relearning physics for the third, maybe fourth, time. You've seen this stuff at least two times before. Don't throw that old knowledge away. Your undergrad classical mechanics class should have covered "Lagrange multipliers, Euler angles (and other rigid body stuff) and Hamiltonian dynamics," just with less rigor and depth than your current class.

Something that works for me is to not have one textbook, and get as many different text books and learning materials as possible. I find it useful to have different people explain the same thing in different ways, since it increases the chances that something will "make sense." There's lots of good material on the internet.

One other resource that I've found useful is wikipedia. Once I do understand something, I usually edit the relevant article on wikipedia since trying to explain what is going on helps me understand it.

Also, if you haven't gotten yourself in a study group, get one. It helps to work through the problems, and also it makes it lot easier to complain about things when everyone else is complaining.

Your undergrad classical mechanics class should have covered "Lagrange multipliers, Euler angles (and other rigid body stuff) and Hamiltonian dynamics," just with less rigor and depth than your current class.

Unfortunately my undergrad mechanics completely omitted Lagrangian mechanics and everything thereafter, so this is the first time, heh.

Unfortunately my undergrad mechanics completely omitted Lagrangian mechanics and everything thereafter, so this is the first time, heh.

That may be a problem since I think that instructor is assuming that you have background that you don't so they aren't going over the basic steps. What I think would be useful is to surf the web and download some course materials from a basic class on Langrangian mechanics and go through that quickly. The wikipedia article is a good place to start and it's a much better explanation for someone that is starting from ground zero.

Undergraduate classes tend to focus on the mechanical aspects (i.e. here is a cookbook method for solving this problem, don't worry too much about why it works), whereas graduate classes tend to focus on the "so this is how the magic works" parts. Something else to do is to look over the curriculum for the next two years, and then look for places where there are holes in your knowledge and self-study before the class starts.

That may be a problem since I think that instructor is assuming that you have background that you don't so they aren't going over the basic steps. What I think would be useful is to surf the web and download some course materials from a basic class on Langrangian mechanics and go through that quickly.

Undergraduate classes tend to focus on the mechanical aspects (i.e. here is a cookbook method for solving this problem, don't worry too much about why it works), whereas graduate classes tend to focus on the "so this is how the magic works" parts. Something else to do is to look over the curriculum for the next two years, and then look for places where there are holes in your knowledge and self-study before the class starts.

We recently finished our Calculus of Variations and Lagrangian/Hamiltonian Dynamics chapters. It's basically modern mechanics and very powerful. We derived a lot of ubiquitous principles, such as conservation of energy, linear momentum, angular momentum, etc.

marcusl
Gold Member
Unfortunately my undergrad mechanics completely omitted Lagrangian mechanics and everything thereafter, so this is the first time, heh.
If Goldstein looks intimidating, try Marion's Classical Dynamics. It's an advanced undergrad text that covers the topics you mentioned at a more leisurely and expository pace, but still with good rigor.

If Goldstein looks intimidating, try Marion's Classical Dynamics. It's an advanced undergrad text that covers the topics you mentioned at a more leisurely and expository pace, but still with good rigor.

Ok, I'll add that one to the list. I'll also peruse my copy of Fowles and Cassiday to see if theres anything helpful in there.

If Goldstein looks intimidating, try Marion's Classical Dynamics. It's an advanced undergrad text that covers the topics you mentioned at a more leisurely and expository pace, but still with good rigor.

That's the book we're using.

marcusl
Gold Member
To be specific, I am familiar with the second edition of Marion (1970). The recent editions by Thornton and Marion seem to get mixed reviews on Amazon.

One other thing about sleep. It's fine to pull an all-nighter before homework is due, but I've found it to be a seriously bad idea to skimp on sleep before an exam.

Thanks for all the tips folks.

D H
Staff Emeritus
If Goldstein looks intimidating, try Marion's Classical Dynamics. It's an advanced undergrad text that covers the topics you mentioned at a more leisurely and expository pace, but still with good rigor.
That is what I used as an undergrad (2nd edition). It occasionally does use a bit less rigor than a more advanced text. For example it uses a hand-wave argument to arrive at

$$\left(\frac{d\vec x}{dt}\right)_{\text{fixed}} = \left(\frac{d \vec x}{dt}\right)_{\text{rotating}} + \vec{\omega} \times \vec x$$

where $\vec x$ is a displacement 3-vector and then generalizes this to all 3-vectors with one sentence.

Pengwuino
Gold Member
That is what I used as an undergrad (2nd edition). It occasionally does use a bit less rigor than a more advanced text. For example it uses a hand-wave argument to arrive at

$$\left(\frac{d\vec x}{dt}\right)_{\text{fixed}} = \left(\frac{d \vec x}{dt}\right)_{\text{rotating}} + \vec{\omega} \times \vec x$$

where $\vec x$ is a displacement 3-vector and then generalizes this to all 3-vectors with one sentence.

SO(3). *Steps into smoke screen*.

Or something.

D H
Staff Emeritus
SO(3). *Steps into smoke screen*.

Or something.
Exactly. Or almost exactly. More like d/dt (SO(3)). Or something.

Marion does not talk about the myriad ways to represent rotations, that rotations in three space are a non-commutative group, that this group generalizes to the concept of Lie groups, that Lie groups are associated with Lie algebras, etc.

marcusl
Gold Member
Guys, it's a junior year undergrad book, so don't expect grad level treatment. I suggested it because llello said he missed out on undergrad mechanics and he needs quick help to un-crush his soul.

Unfortunately my undergrad mechanics completely omitted Lagrangian mechanics and everything thereafter, so this is the first time, heh.

That sounds like terrible judgment on the part of your undergrad professor. In my mechanics class (undergrad, which I'm taking now), my professor stated that Lagrangian mechanics was the most important thing in the course, and we spent a good month on the topic.

Don't short your self too much on the sleep. I know you know this, and I knew it too when I was in school. But I still chose to study rather than sleep, and I really regretted it. It severely limits your creativity and speed of learning.

Very sound advice, i wish someone told me this 5 years ago.

D H
Staff Emeritus