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Work and motion strategies to a problem

  1. Dec 28, 2009 #1
    1. The problem statement, all variables and given/known data

    So the problem is getting at a basic understanding of the work energy theorem, and just asks for the work done by gravity at a ball's max height if the ball (with mass 0.25 kg) is thrown into the air with initial velocity of 30 m/s. using W=change in KE, the answer is -112.5 J

    But if I use the formula vf^2 = vi^2 + 2ad, to determine d, I get d as approx. 46, and so W=294 x 46 = 13524 J ??



    2. Relevant equations





    3. The attempt at a solution
     
  2. jcsd
  3. Dec 28, 2009 #2
    Where did 294 come from? And 46 what? (units!)
     
  4. Dec 29, 2009 #3
    right, 46 meters. and the 294 (N) was the force calculated as mxa = 30 kg x 9.8 m/s2
     
  5. Dec 29, 2009 #4
    You said the mass is .25 kg, not 30 kg
     
  6. Dec 29, 2009 #5
    haha, right. not sure why my brain did that.
     
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