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Homework Help: Kinematics Equations (2 Problems!)

  1. Sep 17, 2008 #1
    1. The problem statement, all variables and given/known data

    In solving a kinematic equation for x, which has a negative acceleration, is x necessarily negative?

    A classmate states that a negative acceleration always means that a moving object decelerating. Is this statement true? Explain.

    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Sep 17, 2008 #2
    No, depends on reference. You can say gravity has a negative acceleration in the y prime, but a falling object is accelerating. The correct term is negative acceleration, not decelerating.

    Note: I could be wrong.
     
    Last edited: Sep 17, 2008
  4. Sep 17, 2008 #3
    Thanks for the help, but it's two problems in my book, and those are the exact words. So I don't know.
     
  5. Sep 17, 2008 #4
    For your first question, what is x? Is it displacement, velocity or what?
     
  6. Sep 17, 2008 #5
    I have no idea. I believe it's displacement, if I'm not mistaken. My teacher and the textbook is really vague and not clear at all :(
     
  7. Sep 17, 2008 #6
    Haha! I know how that is...

    The answer is NO. This is because x could have a positive displacement and could also have a negative acceleration (slowing down) at the same time. Example, you roll a ball on the floor. It moves away from you (positive displacement) but is also slowing down (negative acceleration).

    Again, I could be wrong, I'm only in last year of high school physics.
     
  8. Sep 17, 2008 #7
    Alright, I'll take that into consideration.
    Thanks alot again! :) Really helped!
     
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