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Homework Help: Football kick

  1. Oct 14, 2009 #1
    1. A football is kicked at an angle of 45 degrees from a distance of 37 meters and just clears a 3 meter high goal on its way down. To the nearest m/s what was its initial speed?

    2. v = v_0 + a*t
    v^2 = (v_0)^2 + 2a*(x - x_0)
    x=x_0 + (v_0)t + (1/2)*a*t^2

    3. I set the original velocity as V and tried to solve but I got a negative number
  2. jcsd
  3. Oct 14, 2009 #2


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    Homework Helper

    Separate the initial velocity v into horizontal and vertical parts. Then write two headings:
    Horizontal and Vertical. Decide in each case whether you have constant speed or accelerated motion and write the appropriate formula(s). Your x = formula is not correct. You don't have a y = formula. Put in the numbers or expressions for all known quantities and try to make progress on all three fronts.
  4. Oct 14, 2009 #3


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    Homework Helper

    First of find the vertical and horizontal components of v_o.
    Displacement is given, . Find time t in terms of v_ox.
    In the last equastion
    y = y_o + v_oy*t - 1/2*g*t^2, substitute the value of t and solve for v_o.
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