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Homework Help: Finding the initial Y velocity, angle, etc from a kicked football

  1. Oct 2, 2006 #1
    The problem is this, you need to determine: The initial Y velocity, initial X velocity, angle reference to the ground, maximum height of the ball, and length of the field goal you should be able to kick.

    I kicked the ball 27 yards, and it was in the air for 2.2 seconds. It was easy to find the initial X velocity, just do Vx = Vi (t) which came out to 11.23 m/s. But how am i supposed to find the Vavg, and or Vy (initial Y velocity) and the angle, when i dont have either of those?

    The formulas available are:

    dx = Vix (t)
    dy = Viy (t) + 1/2 (ay) (t[squared])
    Vfy[squared] = Viy[squared] + 2(ay)(dy)

    Vxi = Vi (Cos[angle])
    Vyi = Vi (Sin[angle])

    Including other basic ones as well, but those are the main ones. How do i go about doing this problem? I think once i find the initial Y velocity and angle, i can figure out the rest of the problem. But this is tricky...

    Thanks in advance, and if anything needs clarified, or was confusing, just ask. Any help at all is very appreciated.
  2. jcsd
  3. Oct 2, 2006 #2


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    Homework Helper

    What does 'a' equal in your 'dy' equation? Which is the acceleration of all 'falling' objecs? Which component of the velocity is constant? The x or the y component? (Hint: in which direction is there no acceleration?)
  4. Oct 2, 2006 #3
    A = accelteration. So Ay is acceleration in the Y direction, which is -9.8 for gravity.

    The X acceleration is constant, because we havent factored in air resistance. (even though its there)
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