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Homework Help: What is the problem?

  1. Feb 18, 2004 #1
    What is the problem??

    Ok, I have been enrolled in my first physics course for about a month now.

    Last week we took a test, and I could not get a final answer for ANY of the problems!!

    I just don't understand why I can't do this stuff.

    So far we have done kinematics, 2 dimensional motion, projectile motion, centripital acceleration, friction and forces.

    I went to get help from my teaching assistant, and he told me he will not give me another lecture.

    So right now I am stuck, and pretty desperate.

    When I sit down to do homework.. I can not get ONE answer.

    In the beggining I sat and did the homework with my friends, but everyone ended up going off on tangents and finishing in their own way, and I ended up copying.

    So I'm pretty sure that I did VERY poorly on this test. Hope comes in that one test is dropped, so I have another chance.

    But obviously the material never gets dropped, so I must learn it.

    I know the best way to learn is to do hundred's of exmaples, but I can't do ANY!!

    I understand like 50% of the concepts, and have problems when it comes to doing a problem.

    I want very badly to understand physics and to do it very well, but I just can't get my feet off the ground.

    I found a tutor that charges $20 an hour, and I went to her a couple of times. I racked up $60 worth of tutoring in one night, and I still couldn't do a problem. My problem with her is that she has a VERY VERY thick accent and it makes it hard for me to understand. She also does problems differently than I've learned.

    Thats another problem. EVERYONE does the same problem a different way. I go to help from one source, and the next source shows me differently.

    I NEED to understand Physics. I want to very badly.

    My question to you guys is: How do I do this? How can I get my feet off the gound and start to be able to do problems. I have no fear of putting in hard work and I am totally willing, but I need a launching pad!

    My next exam is in the middle of March. I plan to work very hard to master that test. But first I need to go back and master the basics.

    How is it done? I somehow need this subject put into perspective. I need a way to find clues so I can know what the problem is asking and how to find the answer.

    Thank you in advance.

    PS - I can provide problems if someone would be willing to help me walkthrough one of them.
  2. jcsd
  3. Feb 18, 2004 #2
    Maxwell, I think your situation is worse than mine. That teaching assistant certainly acted meanly.

    Post specific problems, these people, Bless Them, will help. Tell them if you know calculus or not. Look back through this forum and in the k-12 one, too, and see if you can pick up some answers that way.

    Is the problem your math skills, do you think? Are you weak in math? You may want to drop the course and next semester, take a math course or courses to get you up to speed. Then, retake the physics course. It sounds like an unattractive option, but please consider it, because math sneaks up behind you your whole life and bite you...well, you know where.

    If math isn't your difficulty, if it's the concepts, these people, Bless Them, can help you very much. I can say, I am able to stay in my course only because of their help.

    So start posting, and good luck.
  4. Feb 18, 2004 #3
    My math skills are actually pretty strong.

    I have taken Calculus and did pretty well in it. I am enrolled in Calculus 2 right now.

    I have not seem any math that has given me trouble thus far.

    My problem is knowing how to set up a problem to do the math! I have no idea where my professor finds the numbers he uses to set up an equation.

    (By the way, this is a Calculus-Based Physics course).

    Thank you for responding, Holly =)
  5. Feb 18, 2004 #4
    This is a strategy I like to use: ask yourself what don't I understand? And don't say "all of it" or "physics". Pinpoint a specific question: "I dont understand Newton's First Law" - and then answer it! An object at rest tends to stay at rest.. well, what does that mean? Unless there is an outside force on it, it will not accelerate.

    And as for the numbers.. you have an equation, let's say

    [tex]W = F \times D[/tex]

    You understand the equation, right? Work is equal to force times the distance. Given a problem "Find the work done by gravity on a 5kg book that falls 10 meters"

    What are you looking for? Isolate that variable. In this case, it is W. So we need F and D. Well, D is distance. What is the distance the force is exerted over? We are only given one in the problem, which is 10 meters (of course in more complicated problems, it may not be stated in the problem.. but we'll leave that for now). So we have D=10m

    Finally, we come to F. Well, we're not given that. So what is an equation you know relating F and M? Why, F=ma. So what is a? It is acceleration; what is accelerating the book? There is no outside force, so you know it must be gravity (9.81 m/s^2). Now we have everything needed to solve the equation: We find the force is mass*gravity, which is 49.05N, and the distance, 10m.

    Plugging in to our original equation, we get the work done is 490.5N

    So, despite my blabbering ( ) - what is my advice? Ask yourself what you know, what you have, and what you're looking for.
  6. Feb 18, 2004 #5
    Maxwell, if you look over in a thread called Formula Mania: Please Give, I asked for formulas, and someone named chroot it was I believe put in a buncha buncha formulas, probably every formula known to man, and since you are adept at calculus, you will understand them. Maybe when you see them you will recognize where the professor is pulling some of those Mystery Numbers from...the constants and so forth used in the equations...worth a look for certain. Then you will feel like this not this next test.
  7. Feb 19, 2004 #6
    Thanks guys, I looked over the thread and there are some good posts there. Chroot's list was awesome, but I only knew a few equations so far.

    I will post some examples tonight.

    Thank you :smile:
  8. Feb 19, 2004 #7


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    Homework Helper

    Maxwell, you are correct that the best way to learn physics is to work through as many problems as possible. Your best bet is probably to post your questions/roadblocks here, since your evil TA is evil.

    Some vague suggestions I will offer since you say you don't even you how to introduce math into your HW/test problems:

    the somewhat obvious:
    - almost always helps to draw a picture (i.e. free body diagram)
    - pin down what you are looking for, what the question is asking for
    - pin down what information is given
    After doing these things listed above, sift through your formulae and consider the ones that contain the variable you want for the answer and the variables that are given to you.

    the not so obvious:
    - determine which assumptions are appropriate and which are inappropriate
    - determine what approximations are appropriate and which are inappropriate
    After you have done these things listed above, eliminate formulae that don't agree with your assumptions and approximations. Almost all of the formulae come with hidden assumptions and approximations. These not so obvious issues are the hard part, but they are also the more sophisticated, less monkey-see-monkey-do part of physics. They require a developed intuition for physics, and so, ironically, you have to work a lot of problems to get them down efficiently. It is kind of like a catch 22, but more like going to rehab (or, I guess it should just be called hab, since it is the first time you have done it). It seems impossible, and you try and try and try and can't even understand how to accomplish the task in principle, until one glorious attempt, you exhert the pivotal effort, and it clicks.
    Last edited: Feb 19, 2004
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