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Acceleration question

  1. Oct 21, 2006 #1
    I've been attempting the following question:

    A 120gram hockey puck sent sliding over ice with an initial speed of 5.5m/s is stopped in 15m by the frictional force on it from the ice.What is the acceleration experienced by the puck?

    I'm getting an answer of 2.0157m/s^2.I'm wondering if this is correct or not?
    Thanks.
     
  2. jcsd
  3. Oct 21, 2006 #2

    Hootenanny

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    If you assume the acceleration is constant then your answer is incorrect. Perhaps if you show your working we could correct you. Also note that the acceleration should be negative since the puck's velocity is decreasing.
     
  4. Oct 21, 2006 #3
    i used the formula vf-vi/tf-ti to get that answer
     
  5. Oct 21, 2006 #4

    Hootenanny

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    And how did you calculate the time?
     
  6. Oct 21, 2006 #5
    i divided 15m by 5.5m.however,i now realise this is wrong as the 5.5m. is INITIAL speed
     
  7. Oct 21, 2006 #6

    Hootenanny

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    Indeed, so if we assume the acceleration to be uniform how does the displacement, initial and final velocity relate to the acceleration?
     
  8. Oct 21, 2006 #7
    sorry,i've no idea.
     
  9. Oct 21, 2006 #8

    Hootenanny

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    No problem, you may want to take a look at these kinematic equations courtesy of Doc Al.
     
  10. Oct 21, 2006 #9
    would it be this equation:v^2=vo^2+2a(x-xo)
     
  11. Oct 21, 2006 #10

    Hootenanny

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    Indeed it would, all that is left to do is some algebraic manipulation and to substitute in your values.
     
  12. Oct 21, 2006 #11
    thanks for all your help.i'm now getting -1.01m/s^2
     
  13. Oct 21, 2006 #12

    Hootenanny

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    Looks about right to me. My pleasure.
     
  14. Oct 21, 2006 #13
    Thanks so much,you're a great teacher!
     
  15. Oct 21, 2006 #14

    Hootenanny

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    Thank you very much :smile: I do my best.
     
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