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Help with easy intagration

  1. Apr 13, 2005 #1
    i am haveing some trouble solvine a simple question
    the question is what is the work done by the equation
    8x-16
    from 0 to 3
    if you intagrate it you should get
    4x^2 -16x
    then you sub in zero get zero then you sub in 3 and get -28?
    yet the answer in the book is -12 am i doing something wrong?
    or is the book wrong?
     
  2. jcsd
  3. Apr 13, 2005 #2
    I think that you made a mistake in your calculations, subbing 3 in gives
    4*(9)-48=36-48=-12 =)
     
  4. Apr 13, 2005 #3
    thanks i knew it was a stupid thing im being an idoit
     
  5. Apr 13, 2005 #4
    Pat yourself on the back for integrating correctly atleast :)
     
  6. Apr 14, 2005 #5
    ya but if i cant times 3 by 16 correctly i think the intergration is the least of my worries
     
  7. Apr 14, 2005 #6

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    Would it be petty of me to point out that equations don't DO work?

    What you mean I presume is that the force is given by F(x)= 8x-16 and moves an object from x= 0 to x= 3.
     
  8. Apr 14, 2005 #7
    You make an interesting point, but keep in mind that many of these problems in math always have an answer that is dimensionless... Yes it is better to write the work done by some force moving a particle... but when the solutions key gives an answer with no units, that really annoys me... so I don't really see anything wrong with saying "the work done by an equation." Same with surface integrals... answers are dimensionless... which is why I like to see applications of math. What does it mean when a surface integral evaluates to "16pi"? What does it mean when the work done is "5" ?
     
  9. Apr 15, 2005 #8
    yes its petty
     
  10. Apr 15, 2005 #9
    Tell me more
     
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