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Homework Help: Negative acceleration - change in direction or slowing down?

  1. May 27, 2009 #1
    1. The problem statement, all variables and given/known data
    Since we can't tell if a value of negative acceleration means a change in direction or decceleration, how WOULD we be able to tell if its a change in direction or the speed is slowing down (say, if we were given v_initial and v_final)?

    2. Relevant equations

    3. The attempt at a solution
  2. jcsd
  3. May 28, 2009 #2


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    Gold Member

    If you're given V_i and V_f you know that some negative acceleration had to occur in the direction of motion. You need more than just velocities however, to determine much of anything about the acceleration. Similarly, if you're just given an acceleration, that doesn't necessarily tell you much about how the velocity changes.
  4. May 28, 2009 #3


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    Homework Helper

    Y'know, a negative acceleration could even mean something is speeding up, if it has a negative velocity (i.e. if it's moving "backwards")
  5. May 28, 2009 #4
    I think it has to do with acceleration being the second derivative of the position vector but I am not entirely sure.
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