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Homework Help: Which Equations constant I use here ?

  1. May 30, 2010 #1
    Hi ALL



    which Equations constant I use here ?



    a truck covers a distance of 50 m in 8 s while smoothly sowing down to a final speed of 2.5 m/s . find its original speed



    Dx = 50 m

    t = 8 s

    v = 2.5 m/s



    Now I take this equation bit I don't now why I didn't get the correct answer





    Dx = (v + v0 ) t/2



    =50 = 2.5 + v0 ) 8 /2

    =2 X 50 + 92.5 + v0 ) 8 /2

    =100 = 20 + 8v0/2

    =128v

    v = -128
     
  2. jcsd
  3. May 30, 2010 #2
    I think you've just added it up wrongly.
    50m = (2.5m s^-1 + v0 ) 8s /2

    is right.
    Solve for v0.
     
  4. May 30, 2010 #3
    but here in my book the answe is 10 m/s

    ??


    they do v0 = 2DX/2-v = 2 X 50 /8 -2.5 = 10

    ??please I want the help beacuse I fell confused

    I wait
     
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