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Homework Help: Force Problem

  1. Jun 14, 2008 #1
    Force Problem!!!!!!!!!

    1. The problem statement, all variables and given/known data
    a ball of mass 2.0kg is dropped from a height of 10m. the speed of the ball is measured as 12.5m/s just before it hits the ground. what was the work done against air friction during this fall?

    2. Relevant equations

    3. The attempt at a solution
    totally lost on where to begin can someone help me start? im not finding anything on work itself as a force, is it a force?
  2. jcsd
  3. Jun 14, 2008 #2
    Work is not force. Exerting a force is not the same as doing work.

    Work = force*distance.
    Last edited: Jun 14, 2008
  4. Jun 15, 2008 #3

    Gib Z

    User Avatar
    Homework Helper

    So in this case, Work = mg * 10m. See what that comes out to first.

    Then, using some basic equations of motion, you want to work out what the speed of the ball would have been, neglecting air resistance. Now, we know what the actual speed was, accounted for air resistance. Then use the formula for kinetic energy to get you to the end =]
  5. Jun 16, 2008 #4
    What is the work done against gravity my friend?
  6. Jun 16, 2008 #5
    so if work is mg*distance
    then would the work be 2.0kg*10m= 20kgm?
  7. Jun 16, 2008 #6
    or 20J, now what is the actual kinetic energy of the ball at the bottom?
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