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General Physics Question

  1. Oct 5, 2008 #1
    Can something be going at negative acceleration be going faster or moving, not stopping or becoming slower?
     
  2. jcsd
  3. Oct 5, 2008 #2

    Doc Al

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    What does "negative" mean?
     
  4. Oct 5, 2008 #3

    mathman

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    "Negative acceleration" sounds like the acceleration vector is in the opposite direction of the velocity vector. Net result: slowing down.
     
  5. Oct 5, 2008 #4
    it depends on the sense of direction
     
  6. Oct 6, 2008 #5
    If the object has positive velocity, but negative acceleration, it is slowing down.
    If the object has negative velocity, but positive acceleration, it is slowing down.
    If the object has positive velocity, and positive acceleration, it is speeding up.
    If the object has negative velocity, and negative acceleration, it is also speeding up.

    Basically, if the acceleration and the velocity vectors are in the same direction, the object is speeding up. If they are in opposite directions, the object is slowing down.

    hope that helps.
     
  7. Oct 6, 2008 #6

    mathman

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    Both velocity and acceleration are 3-d vectors, so positive and negative don't have any real meaning for them seperately, only relative to each other.
     
  8. Oct 6, 2008 #7
    I apologize, what i said earlier applied to one dimension only. For 2 or 3 dimensions, you have to break down the acceleration and velocity vectors into x and y or x, y, and z components, respectively.

    Then you have to have a defined +x and -x. same goes for y and, if youre in three dimensions, z.

    then the rules i stated above apply, but you have to keep in mind that they apply only in that dimension. simply because both the velocity and acceleration vectors for x are positive does not necessarily mean it is speeding up. you need to take into account the other dimension(s).
     
  9. Oct 6, 2008 #8

    Redbelly98

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    Doesn't the wording of the question -- "...negative acceleration..." -- imply we're discussing 1-dimensional motion?
     
  10. Oct 6, 2008 #9
    Thats what i assumed, but i guess mathman thought that the OP was in more dimensions...
     
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