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Homework Help: Sports Car Acceleration Question

  1. Jan 14, 2010 #1
    1. The problem statement, all variables and given/known data
    A sports car moving at constant speed travels 110m in 5.0s. If it then brakes and comes to a stop in 4.0s. what is its acceleration in m/s^2? Express the answer in terms of "g's." where 1.00 g = 9.80 m/s^2.

    2. Relevant equations
    I thought about using the equation a=v/t

    3. The attempt at a solution
    So I tried it sort of I am just sort of lost I am not really sure how to start....
  2. jcsd
  3. Jan 14, 2010 #2


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    Homework Helper

    You need to use the kinematic equations




    Which one do you think you will have to use?
  4. Jan 14, 2010 #3
    What does the u stand for, that's not in my book?
  5. Jan 14, 2010 #4
    The car initially had a velocity of 110m/5s (22m/s) and came to a stop (0m/s) in 4.0s. The acceleration is the change in velocity over a time interval.
  6. Jan 14, 2010 #5
    So would we use the v=u+at since I have the 4.0s and the 22m/s? but what would go in for the u?
  7. Jan 14, 2010 #6
    u is initial velocity and v is final velocity.
  8. Jan 14, 2010 #7
    Okay I figured it out thanks so much the answer was -5.5 m/s^2 and then in g's it was -0.56 g's
  9. Jan 14, 2010 #8
    take u (initial speed) = 110 / 5 = 22m/s
    v = 0
    t = 4

    v = u + at
    0 = 22 + 4a
    4a = -22
    a = -5.5m/s^2
    a = (-5.5/9.8)g = -0.56g
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