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Homework Help: Work-Energy Method

  1. Oct 31, 2007 #1
    [SOLVED] Work-Energy Method

    1. The problem statement, all variables and given/known data

    A car is stopped by a constant friction force that is independent of the car's speed. By what factor is the stopping distance changed if the car's initial speed is doubled? (Solve using work-energy methods.)

    2. Relevant equations

    Wtotal = delta K

    3. The attempt at a solution

    From what the problem is stating, is that friction force, is seperate from car's speed.
    ''if the car's initial speed is doubled?''
    K1 = 1/2(m)(2v)^2

    I know the answer is 4, but I don't comprehend, what is the car's initial speed is tripled, would it be 6?
  2. jcsd
  3. Oct 31, 2007 #2

    Doc Al

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    Staff: Mentor

    How does stopping distance relate to kinetic energy?
  4. Oct 31, 2007 #3
    well if the velocity is higher, then it would be harder to stop at a shorter distance than a long one.
  5. Oct 31, 2007 #4

    Doc Al

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    Staff: Mentor

    I'm looking for a precise answer. What factors affect stopping distance? Give an equation.
  6. Oct 31, 2007 #5

    W = F*s

    s being distance

    and work total = k2-k1

    so, k2-k1 = F*s
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