# Is mechanics supposed to be this hard?

Gold Member
From what I've experienced so far, classical mechanics (well, newtonian since I'm still on K&K) is very difficult. It gets even harder because I have no teacher and my next math class is honors algebra 2 (I already know calculus though). I'm able to solve problems (I'm on chapter 3 about applying Newton's laws) but only barely because I almost ALWAYS get it wrong before looking at the hint or answer. Is everything else I study after this (E&M, QM, Thermo) going to get easier over time or does it all get harder? I'm wondering how I'm going to go through Griffiths and Purcell when I find K&K this hard. I'm not giving up though, as I can't see myself doing anything other than physics.
Will everything just get harder? Because keeping up is slowly being a problem; e.g I have to spend much more time on a couple of problems now than I did before.

jbunniii
Homework Helper
Gold Member
I've only seen a couple of your threads, so it's hard to extrapolate. Based on the ones I've seen:

it seems to me that your problems are more algebraic than conceptual. My recommendation would be to double check each step carefully, and write out all the steps rather than trying to juggle the algebraic manipulations in your head. Also, at each step, do some basic "sanity checking" to make sure the equation makes sense: are the units of each term correct, etc. Be careful with signs, both in the algebra and when translating force diagrams into equations. Don't worry, we all make dumb algebra errors, even after studying math for years. The key is to have the discipline to proceed methodically and proofread your work.

WannabeNewton
I can't do math to save my life. That being said, I've personally found certain physics classes (not necessarily physics itself) to be considerably easier when compared to the Klepper + Purcell sequence, such as QM (Shankar) and advanced EM (Marion and Heald), and other classes to be just as hard if not harder, such as GR and stat mech. So it's not a black and white issue.

1 person
Gold Member
I've only seen a couple of your threads, so it's hard to extrapolate. Based on the ones I've seen:

it seems to me that your problems are more algebraic than conceptual. My recommendation would be to double check each step carefully, and write out all the steps rather than trying to juggle the algebraic manipulations in your head. Also, at each step, do some basic "sanity checking" to make sure the equation makes sense: are the units of each term correct, etc. Be careful with signs, both in the algebra and when translating force diagrams into equations. Don't worry, we all make dumb algebra errors, even after studying math for years. The key is to have the discipline to proceed methodically and proofread your work.
So I'm understanding the physics conceptually, just making mathematical errors.

I can't do math to save my life. That being said, I've personally found certain physics classes (not necessarily physics itself) to be considerably easier when compared to the Klepper + Purcell sequence, such as QM (Shankar) and advanced EM (Marion and Heald), and other classes to be just as hard if not harder, such as GR and stat mech. So it's not a black and white issue.
So doing crappy (pardon the language) in K&K and Purcell (and by crappy I mean getting no questions correct in the first or second try and not getting some questions at all) is normal? I feel like I'm not doing so well in physics anymore. Well, at least after I left the Halliday-Resnick and all the other easy texts. Will I be able to continue self learning or is there a point where you need to get a teacher? Because so far, things are only getting harder and there's less productivity because of slower pacing.

jbunniii
Homework Helper
Gold Member
So I'm understanding the physics conceptually, just making mathematical errors.
As I said, I am only working with a data set of two threads, but that's how it looks to me. Certainly you are making algebra mistakes that are tripping you up, and that can easily cause you to get wrong answers frequently even if you are conceptually OK... which can lead you to think you are misunderstanding the physics even if you are not.

Anyway, just keep posting whenever you even slightly doubt your reasoning or your answer. I'm also self studying K&K and have posted several threads and received very useful feedback so far. If you are making any conceptual errors, someone will notice them for sure.

1 person
Gold Member
As I said, I am only working with a data set of two threads, but that's how it looks to me. Certainly you are making algebra mistakes that are tripping you up, and that can easily cause you to get wrong answers frequently even if you are conceptually OK... which can lead you to think you are misunderstanding the physics even if you are not.

Anyway, just keep posting whenever you even slightly doubt your reasoning or your answer. I'm also self studying K&K and have posted several threads and received very useful feedback so far. If you are making any conceptual errors, someone will notice them for sure.
Then I'll do just that and hope I can keep advancing in physics :thumbs:
Still though, I must admit that its getting complicated quite early.

jbunniii
Homework Helper
Gold Member
Then I'll do just that and hope I can keep advancing in physics :thumbs:
Still though, I must admit that its getting complicated quite early.
K&K has a reputation as a challenging book, so there's no reason to expect it to be easy. There is no plugging and chugging, and not much repetition: each problem is different from the others, requires some thought, and is illustrating a different point. A trained monkey could probably crank out 50 Halliday problems while we ponder through 5 K&K problems, but who wants to do 50 problems (or to be a trained monkey) anyway?

jtbell
Mentor
K&K has a reputation as a challenging book, so there's no reason to expect it to be easy.
Especially for someone who's still in high school.

AlephZero
Homework Helper
So I'm understanding the physics conceptually, just making mathematical errors.
Maybe, but from those two threads, you are making too many "simple" math errors, so it hard to be sure. You are ambitious to get on to more advanced physics, and there's nothing wrong with being ambitious, but you have to learn to walk before you can run. If solving a problem in K&K takes say 10 steps of math, and you are making mistakes every 2 or 3 steps, you are never going to get the "right answer" first time. I think the best way to fix that is to work on your math till you only make a mistake every 50 or 100 steps, and then go back to learning physics.

K&K has a reputation as a challenging book, so there's no reason to expect it to be easy. ...
A trained monkey could probably crank out 50 Halliday problems while we ponder through 5 K&K problems, but who wants to do 50 problems (or to be a trained monkey) anyway?
I agree 50 doing almost identical problems is too many, but if the OP is having trouble with the math, it could be useful to do a lot of short problems rather than a few long ones. That way you are more likely to get the math "right first time" on at least some of them, which will improve your confidence and motivation. When "all" the problems in Halliday is too easy, and you are getting all of them right, then go back to K&K and Purcell.

1 person
Gold Member
Maybe, but from those two threads, you are making too many "simple" math errors, so it hard to be sure. You are ambitious to get on to more advanced physics, and there's nothing wrong with being ambitious, but you have to learn to walk before you can run. If solving a problem in K&K takes say 10 steps of math, and you are making mistakes every 2 or 3 steps, you are never going to get the "right answer" first time. I think the best way to fix that is to work on your math till you only make a mistake every 50 or 100 steps, and then go back to learning physics.

I agree 50 doing almost identical problems is too many, but if the OP is having trouble with the math, it could be useful to do a lot of short problems rather than a few long ones. That way you are more likely to get the math "right first time" on at least some of them, which will improve your confidence and motivation. When "all" the problems in Halliday is too easy, and you are getting all of them right, then go back to K&K and Purcell.
I'll try and do that; I've got to somehow get my math up to speed.