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Math Help - speed

  1. #1
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    speed

    (a) A car traveling at a speed of v can brake to an emergency stop in a distance x. Assuming all other driving conditions are all similar, if traveling speed of the car doubles, the stopping distance will be (1) √2x, or (2) 2x, or (3) 4x: (b) a driver traveling at 40.0 km/h in a school zone can brake to an emergency stop in 3.00 m. What would be the braking distance if the car were traveling at 60.0 km/h.
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  2. #2
    Bar0n janvdl's Avatar
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    Quote Originally Posted by twistedmexican View Post
    (a) A car traveling at a speed of v can brake to an emergency stop in a distance x. Assuming all other driving conditions are all similar, if traveling speed of the car doubles, the stopping distance will be (1) √2x, or (2) 2x, or (3) 4x: (b) a driver traveling at 40.0 km/h in a school zone can brake to an emergency stop in 3.00 m. What would be the braking distance if the car were traveling at 60.0 km/h.
    s = ut + 0.5 a t

    If  t and  a stay the same, then i would say that  s is directly proportionate to  u .

    Therefore the stopping distance is  2 \ times \ greater

    ----------------------

    For question b)

     v^2 = u^2 + 2as

    40 km/h = 11.1111111 m/s

     0 = (11.11111)^2 + 2(a)(3)

     a = -20,5 m/s^2


    60 km/h = 16,67 m/s

     0 = (16,67)^2 + 2(-20,5)(s)
     s = 6,77 m
    Last edited by janvdl; July 5th 2007 at 11:29 AM.
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