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Homework Help: Antiderivatives and motion

  1. Jan 18, 2012 #1
    1. The problem statement, all variables and given/known data
    A stone is thrown up at 30 m/s from the edge of a bridge 210 m above the river below. How many seconds elapse between toss and splash?



    2. Relevant equations



    3. The attempt at a solution
    dv/dt=-9.8
    v=-9.8t+c2
    30=-9.8(0) + c1
    c1=30

    v=-9.8t+30
    h=-4.9t^2+30t+c2
    210=-4.9(0)^2+30(0)+c2
    c2=210
    h= -4.9t^2+30t+210

    i'm not sure if i'm doing this right/what to do next if i am
     
  2. jcsd
  3. Jan 18, 2012 #2

    berkeman

    User Avatar

    Staff: Mentor

    Yes, your last equation looks okay to me. You've defined h=o at the surface of the water, which is fine. Solve for the time it takes for h to reach 0...
     
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