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Thread: physics homework

  1. July 4th 2007, 09:20 AM #1
    twistedmexican
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    physics homework

    An experimental rocket car starting from rest reaches a speed of 560 km/h after a straight 400-m run on a level salt flat. Assuming that acceleration is constant, (a) what was the time of the run, and (b) what is the magnitude of the acceleration?
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  2. July 4th 2007, 11:44 AM #2
    janvdl
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    Quote Originally Posted by twistedmexican View Post
    An experimental rocket car starting from rest reaches a speed of 560 km/h after a straight 400-m run on a level salt flat. Assuming that acceleration is constant, (a) what was the time of the run, and (b) what is the magnitude of the acceleration?
    Let's do b) first.

    v^2 = u^2 + 2as

    v = 155,5 m s^{-1}

    24197,5 = 0 + 2a(400)

    a = 30 m s^{-1}


    Now a)

    v = u + at
    155,5 = 0 + (30)t
    t = 5,18
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