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2d kinematics problem

  1. Sep 9, 2010 #1
    1. The problem statement, all variables and given/known data
    A stone thrown horizontally from a height of 6.02m hits the ground at a distance of 13.90m. Calculate the initial speed of the stone. Neglect air resistance.

    2. Relevant equations
    1. v = v0 + at
    2. x = x0 + (1/2)(v0+v)t
    3. x = x0 + v0t + (1/2)at^2
    4. v^2 = v0^2 + 2a(x-x0)

    3. The attempt at a solution
    First I solved for t using the y components of equation 3. So
    0 = x0y + (1/2)at^2;
    a = -g;
    x0y = 6.02;

    so t = 1.23s

    Then using x components of equation 2 I said
    v0x = vx;
    13.9 = v(1.23);
    so v = 11.3 m/s

    but that's not the right answer.

    Sorry this isn't more clear, I'm in a hurry. Thanks.
  2. jcsd
  3. Sep 9, 2010 #2


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    Homework Helper
    Gold Member

    I don't think this part is right. Double check your calculations. (And don't forget to take the square root before arriving at your final value for t. :wink:)
  4. Sep 9, 2010 #3
    omg, I swear I went over this problem 100 times and didn't catch that. Thanks.
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