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Testing Solving difficult physics problems on exams.

  1. Oct 31, 2011 #1
    How exactly would be the best method in approaching them? It is not so much solving them that bothers me, but the fact that I am pressed for time. It becomes infeasible to draw diagrams, free-body/motion diagrams, listing knowns and unknowns, and then starting the analysis to solve 1 out of 13 problems with only one hour left. Any advice on this? How do you tackle problems in exams you've never seen before but yet don't have all the time in the world to solve them? Is it better in those cases to just mindlessly "plug-n-chug"?
  2. jcsd
  3. Oct 31, 2011 #2


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    Staff: Mentor

    Which course are you taking?
  4. Oct 31, 2011 #3
    Introductory physics I.
  5. Oct 31, 2011 #4
    Practice, practice, practice, and more of it. I always begin by drawing a picture. A lot of the time this picture is merely a box, with force vectors acting on it. You'd be surprised how good you can get at drawing boxes.
    Moreover, do you understand what is being asked? If you cannot absorb the question instantly, display an array of formulas that pertain to the particular problem, and asses the values that are given in the problem. Are all of these values relevant? What assumptions are being made?
    Lastly, rest easy before an examination and eat healthy food. It takes practice to become good at these topics; some more than others, but nonetheless it takes practice.
  6. Oct 31, 2011 #5


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    Science Advisor
    Homework Helper

    That depends whether you want to learn some physics, or just scrape through your exams.

    But the "mindless" approach may not work anyway if you are being set good exam questions which test if you understood the material, and not just if you can memorize how to do the questions on last year's exam paper.

    It could be that Mechanics is the first course you have taken where you need apply a few general principles to a large range of situations. You had better get used to doing that, because that's the way most of your courses will be from now on.
  7. Oct 31, 2011 #6
    The more problems you practice the more you get a feel for what diagrams you need to draw, what variables you need to solve for, etc. You'll develop an intuition to the problems so that they amount to almost plugging and chugging since you'll know how everything fits together.

    Im a bit confused, If you can solve the problem correctly by simply plugging and chugging then whats the problem. Why draw diagrams and list unknowns if you already know how to get to the answer?
  8. Oct 31, 2011 #7
    Again, drawing two diagrams for both objects and then two free-body diagrams can take major time away from the analysis of the question. Usually, these are the types problems that tend to be complex, problems with forces acting on two masses.

    Eventually, working through so many dynamics problems, I am seeing a recurring pattern in which you have two equations and two unknowns and are constantly solving for those two unknowns, while some other variables cancel out. Wouldn't it be better to just use these shortcuts on exams rather than starting every question from scratch and writing out Newton's second and third laws for every component of every mass?
  9. Oct 31, 2011 #8
    I enjoy working through problems and I have never "plugged-n-chugged" since high school. I'd even prefer exams with 4 very very difficult questions and work through them systematically, but unfortunately my exams are not structured like that. When you have 13 questions to get through, it is not feasible to draw diagrams for all of them and write out Newton's second and third laws and list the knowns and unknowns. That's what happened to me last time and is the main reason why I received such a low mark.
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