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How far does the car travel before stopping?

  1. Nov 15, 2008 #1
    1. The problem statement, all variables and given/known data

    Car: mass = 200g
    Moving at 30 m/s
    Braking force of 10000N.
    How far does the car travel before stopping?

    2. Relevant equations
    W=m x N
    w = F (delta x)


    3. The attempt at a solution
    I found work, (2000)(10000) = 20,000,000
    Then rearranged the second equation to get delta x, and got 2000 as my answer. The answer is 90m and I'm not getting it. Any suggestions?
     
  2. jcsd
  3. Nov 15, 2008 #2
    You can go one of two routes:

    (1) [tex]\vec{F}=m\vec{a}[/tex] and [tex]\vec{v}_f^2=\vec{v}_i^2+2\vec{a}\Delta x[/tex], or

    (2) [tex]\Delta E_k=\vec{W}[/tex], where [tex]\vec{W}=\vec{F}\Delta x[/tex].
     
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