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Homework Help: Kinematics - Find acceleration

  1. Sep 3, 2006 #1

    888

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    hi,
    i need help on a question... if a car stop in a distance of 50m from the speed of 80 km/h how do you find the acceleration is m/s/s? thanks
     
  2. jcsd
  3. Sep 3, 2006 #2

    Kurdt

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    What equations of motion do you know? How about rearanging:

    [tex] v^2=u^2 + 2as[/tex]
     
  4. Sep 3, 2006 #3

    888

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    i've never used that equation before but all the other equations i know are for constant acceleration or average velocity
     
  5. Sep 3, 2006 #4
    Well what equations do you know?
     
  6. Sep 3, 2006 #5

    Kurdt

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    The equation I put up was for constant acceleration and speeds.
     
  7. Sep 3, 2006 #6

    888

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    the equations that i know are: aver. v= v2+v1/2
    x2= x1+v1t+.5at^2
    v^2=V1^2+2a(x2-x1)
    v2= v1+at
    those are only for constant acc.

    aver acc= v2-v1/t2-t1
    aver. vel.=x2-x1/t2-t1
     
  8. Sep 3, 2006 #7
    This is the same equation as Kurdt posted above, and it is the one that you should use to solve this problem.
     
  9. Sep 3, 2006 #8

    Integral

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    Thats just fine because you are looking for the constant acceleration.
     
  10. Sep 3, 2006 #9

    888

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    however the question doesn't say it's looking for constant acceleration
     
  11. Sep 3, 2006 #10
    But it does say to find the acceleration, and unless you know how to find a non-constant acceleration you should just assume that you are looking for constant acceleration.
     
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