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Courses Elementary physics courses - 95% about knowing formulae?

  1. Jan 9, 2010 #1
    Is it just me or does just knowing a few physics formulae make first year physics courses ridiculously easy? I have a few sample tests in front of me and just about every single question can be answered by applying 1 of about 10 formulae in one way or another. I always liked physics but only recently I got my algebra up to scratch and now that I can rearrange any formula I can do just about every one of these elementary kinematics and dynamics question I get. I know a good few people that don't like physics and think its hard. Ive been telling them all they have to do is memorize a few formula and they're set but they don't seem to believe me.
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  3. Jan 9, 2010 #2
    I don't think that that is all there was to it. Of course, if that WERE the case - physics would be a lot "easier". But physics isn't just math, you should be able to account for anything that would be happening "in real life" and factor those considerations in your equations.. If what you say were really the case, freshman physics would truly be easy - it would just be a course with a ton of calculus drill problem, then most math students would just be able to blaze through it, but it isn't the case
  4. Jan 9, 2010 #3
    Funnily enough I find maths the hardest subject of them all and physics the easiest. I think its about visual thinking. Every physics problem I come across I make a mental picture of whats going on then I usually know how to approach the problem. In maths I can't use that approach unfortunately. Even when it comes to electricity and magnetism you can still make mental images by pretending that the electrical charge/magnetic field is visible. I've heard people say "some people just have a head for physics, some don't". Thats ******** in my opinion. Its all about how you approach the subject I think.
    Last edited: Jan 9, 2010
  5. Jan 9, 2010 #4

    Physics Monkey

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    Hi BogMonkey,

    I'm glad that you find physics easy and enjoyable! Knowing formulas can't hurt, but I suspect your strategy of making a mental picture is also a big part of it. You mentioned difficulty doing the same thing in mathematics. I've often found it helpful to translate math problems into physics problems and then apply my physics intuition. It's not always easy or possible, but I think it helps one understand both subjects a bit better.

    An amusing book you might enjoy along these lines is "The Mathematical Mechanic" by Mark Levi.
  6. Jan 9, 2010 #5
    You have to other threads here in which you show why relying on formulas without thinking does not work in physics problem solving.
  7. Jan 9, 2010 #6
    If I had to name one thing like that, instead of saying "knowing formulas", I would say "classify problems by types and their special cases". The first question is: what category and subcategory is this problem in?
  8. Jan 9, 2010 #7


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    I would say you're right, but with the caveat that knowing formulas is more involved than just, well, knowing formulas :tongue2: It's not enough to just have memorized which variables go together in which ways; you have to really know what they mean, and how to identify which physical concepts correspond to the variables. But once you get that, there really aren't that many independent formulas. Heck, all of kinematics is pretty much based on just two formulas, [itex]x = x_0 + v_0 t + \frac{1}{2}at^2[/itex] and [itex]v_2 = v_0^2 + 2ad[/itex]. That plus [itex]F=ma[/itex], [itex]K=\frac{1}{2}mv^2[/itex], [itex]U=mgh[/itex] accounts for elementary dynamics. So I definitely understand what you're saying. I think once you get to the point where physics looks this easy, it means you're in good shape.
  9. Jan 9, 2010 #8
    BogMonkey, I'd say that either your elementary physics class is really easy, or you've gotten to the point where you understand the basic principles very well. When I was in basic physics, it was actually a very difficult class, because I found that the formulas were worthless if you didn't know what to do with them. And that required knowing the physics. A couple years back when I taught elementary physics, I basically told my students flat out that I'm going to give them all the formulas, and that all of their credit would come from working the problems out. So I think that there's a lot more to basic physics than just knowing formulas.
  10. Jan 9, 2010 #9
    No, physics is not about formulas. Plug and chug is not physics. I recommend getting some physics books or look at some physics contests.

    [itex]v_2^2 = v_0^2 + 2ad[/itex] :biggrin:
  11. Jan 10, 2010 #10


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    [tex]v^2 = v_0^2 + 2ad[/tex] actually is what I meant... typo on my part.
  12. Jan 10, 2010 #11

    Vanadium 50

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    There is a subset of students whose strategy is "just memorize the formula". They do very well up to a point, and then hit a wall. Depending on the student's memory, the wall can be in different places - but it's always there.
  13. Jan 10, 2010 #12
    That happened in my AP Physics class last year.

    People basically memorized everything, then the teacher told us he would put a question regarding a car on turning on a sloped bank
    and some people tried to memorize the handful of terribly long equations for friction or minimum velocity.

    A few of them actually got it right, but the teacher only gave them one point :)
  14. Jan 10, 2010 #13
    People that have great memorization seem to be much better in pre-med than undergraduate physics. I have the opposite problem, my memorization is truly awful, so if you have something that requires rote memorization, I'm pretty much dead in the water. I can sometimes "fake memorization" by finding the rule, telling a story, drawing a picture, or looking up the answer on google, but in situations where I have a list of things that just have to be memorized, I'm pretty dreadful.

    One of the tricky parts in teaching is to realize that what may be trivially obvious to you may be completely missing in the student that you are talking to.
  15. Jan 11, 2010 #14
    Knowing the correct formulae will indeed get you through many classes. Recently, however, I took a graduate level physics class (I am an engineering graduate) with a really innovative fellow who crafted his final exam to contain no equations and asked us to do things like explain phenomena based on some empirical data that he provided or asked what would happen if a given situation were perturbed in some way.
  16. Jan 11, 2010 #15
    Surprisingly enough, most of elementary science is plug or chug, but one will realize in the end that the mathematical base that makes the elementary science so science is in fact everything but elementary. A more complex task consists of explaining to yourself why a certain formula works and applying it to other scenarios and other sciences.
    It really depends on the aspect you take in the science.
  17. Jan 12, 2010 #16
    If that is what you learn during your elementary physics courses then the less elementary physics courses will get hard. Somewhere you got to start learning things properly and there is no reason to not start with it during your elementary courses. Sure it takes a bit more time, but you earn all of that back very quickly if you intend to study more later.
  18. Jan 12, 2010 #17

    To the OP: No, elementary physics isn't about knowing formulae. Passing exams and getting good marks is probably attainable (depending on the lecturer..) through basically just knowing a list of formulae. However, understanding concepts is by far the most important part of introductary physics. It means that when you come to tackle more difficult topics later on you'll have a solid background - you'd be amazed to discover how often simple concepts like a pendulum or spring become useful in different areas of physics.
  19. Jan 12, 2010 #18
    Although memorization of formulas is very helpful in physics, when you get to upper level physics courses it will actually become an obstacle. Upper level physics courses require you to derive formulas rather than memorize them. At my university for example the elementary physics courses are a piece of cake if you just know how to work with the formulas. However, when you take the upper level courses such as quantum, most of the questions on the exams and homework will involve you to derive your own equations and learn how they work.

    Summing it up, as you get into more advanced physics and science courses in general you will realize that there isn't a formula for every scenario and that's when your problem solving abilities and knowledge of concepts will come into play.
  20. Jan 14, 2010 #19
    You really only need to know F=ma. You can derive everything else from that (with a few relations needed for circular motion and Inertia, I suppose)

    I don't know why the theory behind the "formulas" doesn't seem to be taught more (my Physics I course was taught as though every formula were completely independent from every other....) but it makes things so much easier.

    I joined a study group one time and it ended up being 90 minutes of me 'showing' the others how they could get any of the formulas from F=ma while they tried to pick out formulas they were certain weren't related in any way.

    I actually made a youtube video showing a few relations (mostly the kinematic equations and Work Energy Theorem) all derived from F=ma. It was before I actually took Physics I, so I don't remember exactly what I showed.
    If anyone is interested it's on the channel of troponinnutrition
  21. Jan 14, 2010 #20
    Memorising equations and formulae may work sometimes, but in the long run you are going to hit a snag unless you really understand what those equations and the question really means.
    Why, I once saw a person posting a problem on electrostatics in the Homework Help forum. He couldn't get the correct answer - having used the value of the Boltzmann constant for that of the constant k often used in Coulomb's Law!
    Multiple step problems also tend to sieve out these plug-and-chuggers from my experience, for there is no one "standard" equation that can output the answer immediately. It's also a good thing to ask for derivations, especially impromptu ones unique to the situation :)
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