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Homework Help: Football Hangtime?

  1. Feb 2, 2009 #1
    The problem statement, all variables and given/known data[/b]
    A football is kicked at ground level with a speed of 18.2 at an angle of 43.1 to the horizontal.

    How much later does it hit the ground?

    Relevant equations[/b]
    I tried using y = y_o + V_o*t + .5(a)(t)^2

    Can anyone help me solve this? It seems like it would be relatively easy but I can't seem to get the correct answer..

  2. jcsd
  3. Feb 2, 2009 #2
    isnt V_o=18.2, and a=43.1 and Y_o=0 (horizontal)?

    and then just plug in and solve for T?
  4. Feb 2, 2009 #3
    wouldn't a = 9.81 m/s^2 (acceleration) ?
  5. Feb 2, 2009 #4
    oh yes, for acceleratoin, and what would the Y_o represent?
  6. Feb 2, 2009 #5
    i was assuming the initial height in the Y direction?
  7. Feb 2, 2009 #6
    which would be zero.. i THINK ur using the wrong formula. I havent done projectile motion in like 3 years, so i was just trying to help out. I remember there was 2 equations though, one if ur starting and ending on the same level, and another if you ur initial height was above the final height... not sure which one you mentioned above..
  8. Feb 2, 2009 #7

    D H

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    Staff Emeritus
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    18.2 what? 43.1 what? The latter is obviously degrees, but you should say so. The former could be feet/second, kilometers/hour, whatever. Now is a good time to get in the habit of placing units everywhere. If you don't you could well end up crashing a spaceship, overdosing a patient, or cause a currency to fail if you are not careful about units.
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