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Homework Help: Basic motion question.Am I correct?

  1. Aug 6, 2010 #1
    1. The problem statement, all variables and given/known data

    A car is traveeling at 50km/h.It has to stop over distance of 100m.
    Find
    (a) constant rate of deceleration neede
    (b)time taken to stop

    2. Relevant equations

    v^2=u^2+2as
    v=u+at


    3. The attempt at a solution

    (a) 50km/hr= 13.889m/s=u
    v=0
    s=100m
    a= need to find

    v^2=u^2+2as

    0^2= (13.889)^2 +2a(100)
    -192.9=200a
    a=-0.9645 m/s^2

    (b)
    v=u+at
    0=13.889-0.9645t
    0.9645t=13.889
    t=14 seconds
     
  2. jcsd
  3. Aug 6, 2010 #2

    Doc Al

    User Avatar

    Staff: Mentor

    Looks perfect to me.
     
  4. Aug 6, 2010 #3
    Thank you so much, Doc Al
     
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