# How to classify problems?

#### djosey

Well i've now read two general "study guides" who advise me to classify physics problems according to their methods of solution or to identify types of problems.

This sounds like a good idea, a good way to start thinking about a problem and take less time solving it, but still being somewhat of a beginner i'm at a loss as to what those types of problems could be. The only thing i can think of is classification by mathematical tools needed (trig, integrals...), but it doesn't sound that interesting. Do any of you do or did something like this, and if yes what kinds of classification do you use?

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#### Feldoh

Well i've now read two general "study guides" who advise me to classify physics problems according to their methods of solution or to identify types of problems.

This sounds like a good idea, a good way to start thinking about a problem and take less time solving it, but still being somewhat of a beginner i'm at a loss as to what those types of problems could be. The only thing i can think of is classification by mathematical tools needed (trig, integrals...), but it doesn't sound that interesting. Do any of you do or did something like this, and if yes what kinds of classification do you use?
Memorizing problems' solutions doesn't teach you how to do physics.

#### Rasalhague

I don't know what it means either. Probably not worth worrying about! Text books often classify their own problems. As you'll have noticed, the easiest, quickest ones tend to come first in a problem set, followed by questions that take more work, involve several distinct steps, offer less guidance, or require the reader to bring together a variety of knowledge and techniques. There may be symbols used to indicate difficulty or whether the problem will need a computer. Some problems are designed to test whether you broadly understand a concept, others your ability to find a detailed solution to a question about a specific example scenario. There are analytical questions versus numerical questions, problems of the kind "prove this general principle, what is the reason, fill in the gaps in the following argument" and problems of the kind "how heavy, how long, what is the force here". I guess it could be useful to think about if you were designing your own problem set or writing a text book. And of course, if you come across an ingenious technique you want to remember, you might want to make a note of it, but the subtle stuff will become instinct the more you do, and the obvious differences are, well, obvious. Might as well spend that time learning more physics!

#### djosey

I don't know what it means either. Probably not worth worrying about! Text books often classify their own problems. As you'll have noticed, the easiest, quickest ones tend to come first in a problem set, followed by questions that take more work, involve several distinct steps, offer less guidance, or require the reader to bring together a variety of knowledge and techniques. There may be symbols used to indicate difficulty or whether the problem will need a computer. Some problems are designed to test whether you broadly understand a concept, others your ability to find a detailed solution to a question about a specific example scenario. There are analytical questions versus numerical questions, problems of the kind "prove this general principle, what is the reason, fill in the gaps in the following argument" and problems of the kind "how heavy, how long, what is the force here". I guess it could be useful to think about if you were designing your own problem set or writing a text book. And of course, if you come across an ingenious technique you want to remember, you might want to make a note of it, but the subtle stuff will become instinct the more you do, and the obvious differences are, well, obvious. Might as well spend that time learning more physics!
Thanks for the advice! i think you're right, not worth worrying about, i wanted to ask in case there was something i missed.

#### djosey

Memorizing problems' solutions doesn't teach you how to do physics.
Maybe i wasn't clear, i know it's not useful to memorize, i wanted to know if i could learn to approach problems more efficiently, that's all.

"How to classify problems?"

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