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Homework Help: Plane motion projectiles

  1. Sep 17, 2008 #1
    1. The problem statement, all variables and given/known data
    A ball is thrown at 60deg with v(subzero) = 20 meters/sec to clear a wall that is 2 meters high. how far away is the wall?

    2. Relevant equations

    3. The attempt at a solution
    I tried inserting my givens into the height equation and came up with a very funky answer. here 'tis:
    h= ((20sin60)^2)/9.8=30.6
    my answer key says x=1.2 or 33.5. I know I'd have to subtract 2 from the number I got, but that doesn't explain the discrepancy between my answer and the one the text gives. what am I doing wrong?
  2. jcsd
  3. Sep 18, 2008 #2


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    Homework Helper

    Your "height equation" is slightly wrong. There's a factor of 2 somewhere you forgot to include.
  4. Sep 18, 2008 #3
    oh--it's supposed to be 2g, right? well, that still gives me 15.3 which is not the answer I'm looking for. I've used this same equation (correctly) on other problems and I'm not sure why this one isn't coming out the same.
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