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Homework Help: Work - unknown variables

  1. Feb 17, 2007 #1
    1. The problem statement, all variables and given/known data

    A force F=bx^3 acts in the x-direction. How much work is done by this force in moving an object from x=0.0m to x=2.2m? The value of bis 3.7 N/m^3

    2. Relevant equations


    3. The attempt at a solution

    Ok since the above equation is true, then the problem would solution would be obtained by simply multiplying our force which is (3.7N/m^3) by the given distance which would be 2.2m. The thing is that once you do that, the problem is over and there is still a variable there bothering us which is x^3. What am I supposed to do with that variable?
  2. jcsd
  3. Feb 17, 2007 #2


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    This is not the force, this is a constant. The force is b*x^3. Since it contains the x^3 term, the force is variable and you can't use W=Fd. Do you know integration?
  4. Feb 17, 2007 #3
    yes, but how would i use it in this case?

    edit: ok i figured it out, it should be the definite integral from 0-2m of F right?
    Last edited: Feb 17, 2007
  5. Feb 17, 2007 #4


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    Yes, but the upper limit is 2.2m, right? :smile:
  6. Feb 17, 2007 #5
    that was exactly it. The answer was 21.6 which rounded up to 22J . Thanks you were a great help!
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