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Changing force lifting a mass

  1. Aug 7, 2007 #1
    1. The problem statement, all variables and given/known data

    A force is exerted by a rope lifting a 2.0kg mass a vertical distance of 10m from the ground. A graphs shows F (N) vs d (m). THe F starts at 20 N and goes to 30 N in a straight line as d goes from 0 to 10m. What is the final speed of the box at 10m?

    2. Relevant equations

    F=ma
    kinematics equations

    3. The attempt at a solution

    I am thoroughly lost as to how to deal with this one. The force applied is not constant, so the acceleration will also not be constant. I'm guessing there is another way of looking at it... would really appreciate a hint in which direction to start... thanks.. the answer is 7.3m/s by the way
     
  2. jcsd
  3. Aug 7, 2007 #2

    Dick

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    Work is equal to the integral over distance of force. Use conservation of energy to compare this with mgh and then use KE=mv^2/2.
     
  4. Aug 8, 2007 #3
    what do you mean work is equal to the integral over distance of force, what is the integral?
     
  5. Aug 8, 2007 #4

    Dick

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    No calculus in this course? Then if you graph force versus distance, work is the area under the curve. That's what an integral is.
     
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