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Physics exams, general advice

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  • Thread starter Redbelly98
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  • #1
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Hey, I just responded elsewhere to somebody who asked for "specific tips on taking a physics exam? Like how to dissect a problem.":


I came up with the following general rules, and am wondering if others want to add to my list? Since no specific course description was given, I am looking for advice that applies to pretty much any physics subject.

  • Be familiar with all the equations you are being tested on, so that you can quickly figure out which equation or equations will apply to any particular problem. Corollary: know which equations do not apply to a given problem.

    Example: "A wire carrying a current of 2.0 A is at 90 degrees to a magnetic field of 5.0 T ..."
    In this case, realize that equations dealing with current I and magnetic field B are relevant. Moreover, equations dealing with a charge q moving at velocity v are not relevant.

  • Be able to draw a diagram to show what is going on pictorially. An example of this is using a free-body diagram to show the forces, including directions, acting on an object.

  • Read the problem carefully, so that you are aware of all information that is being given you. Sometimes purely verbal information is actually conveying numerical information. Example: "An electron ..." means "a charge with q=-1.60x10-19C and mass m= 9.11x10-31kg..."

Answers and Replies

  • #2
During exam:
- Review the solutions as many times as possible (don't simply do it and hand in)

Few days before exam:
- Do past exams from the same instructor if possible

- Do lots of questions!
  • #3
Lifesaver: Remain as calm as you can. (For any exam)
  • #4
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Redbelly98's guidelines are very good. Another piece of essential guidance is Read and follow instructions carefully. Many Physics or other science instructors test and expect conformance to this and assign test item scores to represent how well students handle specific instructions about a test item. Fail to round an answer as directed - lower score; fail to keep result purely in symbolic form if directed - lower score or no score; missing units or not answer in the units asked for - lower score.
  • #5
Never hand in your paper early even if you think you're done. Go over the solutions carefully and read all the problems and directions again. I've made so many mistakes that would have been easy to fix if I'd reread the problems.
  • #6
Polya has written a fascinating book on how to solve mathematical problems, however much of the advice is easily applied to problems on exams and tests. You might of heard of the book its called "How to solve it." I'd definitely check it out on the method of solving problems.
  • #7
Good advices. I think it also depends on the courses and the porfs' exam style.
For instance, I have met some professors like to give problems that one needs to started from the very definition and work them through. And these are normally considered to be the hard problems (or maybe I am just not smart enough; or this is just my tactic while facing those problems I don't know how to solve at my first glance).
I think most of the Physics I exam could be solved by diagram, and plug in either F = ma, energy/momentum conservation.
And reread the hw. Some of the exam problems would be similar to hw, and going over them could warm up one's brain and let one know his or her errors.
  • #8
Cool advice, thank you
  • #9
The advice I give to students is:

1) Learning physics is one thing, practicing exam problems over and over again in order to score a bit higher is another thing.

2) Exam problems are determined by taking the lowest common denominator of the level of students and then subtracting 20%. So, if you just make sure you have mastered the topic at a high level, you don't have to worry about the exam.

3) The best way to study physics is by solving difficult problems. Always make sure that you can derive everything from first principles. From time to time, take a blank sheet of paper and then derive from first principles, without looking in the book, all the important formulas/theorems.

4) Just before the exam look at a few previous exams. You should find that the problems are very easy.
  • #10
Redbelly said it pretty well.

If you come to a problem, and you have no clue initially how to approach it, then skip it and come back later. Having tunnel vision can wreak havoc. Take care of what you do know first, which will ease the pressure associated with the time constraints of the test.

If time is left over, don't leave but carefully check your work.
  • #11
Set up a proper coordinate system for certain questions!

Watch a movie on the last day :P.
  • #12
Be calm, be cool. Don't freak out when you see the test. Remember, other people are having just as hard a time with it. If you paid attention in class and did the homework, you'll be fine.

Confidence is key. I like the suggestion of knowing how to derive things... this is a great technique because it provides flexibility.

I would almost say that, when studying for upper-level physics classes, study the math that's involved rather than / along with the physics. In my experience, lots of physics exams work by giving you problems that require a bit of mathematical skill, and being strong with the math will help you out.
  • #13
Never hand in your paper early even if you think you're done. Go over the solutions carefully and read all the problems and directions again. I've made so many mistakes that would have been easy to fix if I'd reread the problems.
I second this to the max. I can't tell you how many times I've lost points because of stupid errors because i missed part of a question or didn't do it correctly.

Also go over the "easy work" that you've completed. I'm talking about the simple calculations such as addition and multiplication. Often times when you are nervous and in a rush during a test you can screw up simple things which throws your whole problem off.
  • #14
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2) Exam problems are determined by taking the lowest common denominator of the level of students and then subtracting 20%. So, if you just make sure you have mastered the topic at a high level, you don't have to worry about the exam.
Oh this is far from typical, at least at the university level! It also somewhat implies that you'll do great as long as you're not the dumbest in the class. Some professors will absolutely manhandle people on tests. One of our professors is notorious for making tests so hard that 50% is considered "good". Some have tests that are nearly impossible to even finish in the allocated time. Thankfully, in those classes, the professors are gentler on grading, but that might not always be the case.

As for my own tips:

1) Look for key words in problems. For example, "near earth" on a mechanics test most likely means you can use the approximation of your potential V = mgh. A "really long" wire can imply in an electromagnetism test that you're dealing with an infinitely long wire. The same in optics, "far away" means somethings probably going to infinity.

2) Be careful of using previous semesters tests to study off of. Case in point, one professor gave very similar tests in our modern physics semester of the introductory physics series. When we took it, we had past tests to study off of. When the classes after us took it, they had our tests and the tests we had from before. This year, however, same deal, the class taking it had all these tests to study off of for their midterm. The tests have always been basically computational problems. They go in to take the test.... all proofs. Needless to say it didn't go well.

3) As previously stated, know the math well. The further in physics you go, the less problems will have answers that you could have simply guessed at.

4) When you get a test, immediately look through the whole thing and do problems that you REALLY know how to do first. You dont want to waste time on a problem you're struggling on while time ticks away on 'gimme' problems.

5) Conservation laws and limits are your friend! If your doing your mechanics test and your 10kg ball on a 10 meter hill falls off that hill and reaches 100m/s, somethings very very wrong with the situation. If you're studying the current in a closed system and your current disappears as a function of time, somethings wrong. I love limits as well. If any field doesn't drop off to 0 as you move infinitely away from the object, something's wrong. This is where real world intuition can help you out immensely!

6) Be careful with conventions. Typically in physics, we take positive square roots when we have the option of taking either of the square roots. That doesn't mean you take only one square root in your average problem though! The example that comes off the top of my head is normalization constants. We typically normalize something so that when we carry out multiplications and such, our basis has length 1. However, when we solve for the normalization constants, we have a positive and negative root. You CAN take negatives, but you have to take negatives every time so you don't wind up with negative probabilities or vectors going backwards and such.

7) Best advice ever, when a test is done, it's done. Stressing over it doesn't magically change your grade. Also, don't stress period. You have a test coming up, you have such and such number of days to study for it. You study for those numbers of days and you take your test. If you fail, you fail, if you pass you pass. I've honestly never heard of someone who can actually "study harder", as if there is a magically button you can press in your mind to accelerate your learning. You study at your own pace and you study as long as time allows you (and never sacrifice sleep for studying, it works against you) and you do your best.
  • #15
Study intelligently.

In my upper level mechanics class I was stressing out at first because the whole thing of mathematical formalism just slapped me in the face and I screwed the first tests. However, after a while, I would ace the tests without studying that much simply because instead of trying to do as many problems I would just try to gain intuition. How do you do this? I think the best way is discussing the problems with your class mates. At least in my college, physics problems are rnot designed for you to scribble a page of Algebra - generally there is a trick behiind everything. Its not like a class of differerntial equations where some problems are designed to be really tedious computations. So practice is important but it is not as important as in math - what is more important is intuition.
  • #16
From someone who just failed an exam due to carelessness and haste, here are some useful advice:

When studying for the exam:

1. Know all the equations and look at all the examples that the professors did in lecture and make sure to understand them. Know not only how to reproduce the answers but to solve much more difficult problems based on the same concepts.

2. Go over old homeworks and exams.

When taking the exam:

1. Read the question thoroughly and understand the question before answering the question. Ask if you don't understand.

2. Understand why you're doing each step and work carefully.

3. Go back and check your answer. Take limits, sanity tests. Make sure that your answer isn't ridiculous and is at least plausible.

4. Don't turn in your test until you have double checked your work (assuming that you finish early, which happens a lot).

5. To second Pengwuino's advice: when the test is done it's done. Don't feel bad if you failed and don't get complacent if you did well. Relax a bit...and then onwards to the next exam...

Caveat: I haven't taken a physics class from the physics department in a long time since I am an engineering student, but the same advice would probably apply to math and physics classes.

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