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Introduction to Physics HELP. I AM LOST

  1. Jan 27, 2009 #1
    ok. i am taking an "INTRODUCTION" physics class. I have never taken physics in my life before.

    the requirements for this class are high school algebra with a C or better (which i got)

    and the guy throws story problems at us and doesnt explain how to solve them or the formulas. is this normal for an introduction class?

    take this for example:
    Consult Multiple-Concept Example 5 in order to review a model for solving this problem. A hot-air balloon is rising upward with a constant speed of 3.08 m/s. When the balloon is 7.51 m above the ground, the balloonist accidentally drops a compass over the side of the balloon. How much time elapses before the compass hits the ground?



    is it just me that's retarded, or are the requirements for this course much higher than they are listed?
  2. jcsd
  3. Jan 27, 2009 #2


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    Homework Helper

    Welcome to PF.

    That's not a difficult problem.

    The balloon has constant velocity up. Then so does the object.

    What if the problem was someone throwing a ball up in the air at 3.08 m/s and they are standing on a 7.8m cliff. How long until it reaches bottom?

    Don't you have an equation that relates distance, initial velocity and time?

    If not:
  4. Jan 27, 2009 #3
    sigh. i guess i really am retarded

    i don't know how to interpret ANY of that stuff. i took high school algebra and geometry and passed with A's. now this stuff is like chinese to me. i guess i should just drop the class
  5. Jan 27, 2009 #4


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    Really, the key to physics is to being in the mindset to solve problems like this. Think about what information is given and what you need to get. Then, there should be some equation you're familiar with relating the desired quantities.

    If you can do this consistently for every single problem you shouldn't have much difficulty. :)
  6. Jan 27, 2009 #5
    do u think i should take calculus first? my friend is taking calculus and he said that he's learning the same stuff. except his instructor actually teaches the stuff instead of throwing notes on the overhead
  7. Jan 27, 2009 #6
    n i have no idea on how the velocity on this is given or w/e. like i said, this is my first time taking physics n i have not taken any math classes in a while... i never learned about displacement, velocity, or acceleration.
  8. Jan 27, 2009 #7
    n i also don't know wtf a magnitude is either. i am very very aggrevated right now, because i have put the text book in front of me, and it is like i am reading spanish over and over again, and trying to figure out what it means. i don't understand a single thing. honestly
  9. Jan 27, 2009 #8
    dont worry i feel the same way
  10. Jan 27, 2009 #9


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    Calculus certainly isn't needed, because it sounds like you're taking a non-calculus based physics class. That isn't to say it isn't helpful, which it certainly is, but it's not necessary. The link LowlyPion posted is a lot of help, but if as you said this looks like spanish to you I'll try to get you started:

    Displacement is difference between two positions. If I am standing at my house and I walk 5m, my displacement is 5m. However, it is not a measure of the distance travelled (for example if I walk 5m away from my house and then back to my house, my displacement is zero).

    Velocity is the speed of an object, how fast it is moving, with a direction indicated. For example, the velocity of my car on the highway might be 50mph North, or 16m/s direct 16 degrees north of east.

    Acceleration, then, is the change in velocity. When you hear car buffs brag about how fast their car goes from 0-60mph, they're talking about its acceleration. If you're speeding up (i.e velocity goes from 10mph to 40mph), slowing down (i.e velocity goes from 40mph to 10mph), or changing direction (i.e velocity goes from 40mph north to 40mph east), you are accelerating.

    Magnitude is simply the number associated with a quantity such as velocity (which is technically known as a vector). Like I said, velocity includes a direction measurement. So consider the velocity 65mph North. The magnitude of this velocity is 65mph.

    Hopefully this makes sense to you, and if you re-read the link LowlyPion posted earlier I hope the variables in those equations take on some meaning.
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