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Need help finding potential energy formula

  1. Mar 12, 2013 #1
    I took the integral of the equation but its wrong, the program does not have a fraction input to put 1/4 properly. I ended up with -x^-1/4(x^4).
    For part b I plugged in 4.5 and turned the number positive to get the answer.
    Did I do something wrong for part a?
     

    Attached Files:

  2. jcsd
  3. Mar 12, 2013 #2
    That you had to turn the number positive should ring a bell.
     
  4. Mar 12, 2013 #3
    If I plugged in 4.5 into the antiderivative then it would be -122 and thats not correct
     
  5. Mar 12, 2013 #4
    What is the relationship between F and U?
     
  6. Mar 12, 2013 #5
    F=U/x
     
  7. Mar 12, 2013 #6
    You need a review on that.
     
  8. Mar 12, 2013 #7
    force is the derivative of potential energy which means the antiderivative of force is potential energy
     
  9. Mar 12, 2013 #8
    That's not exactly correct. Why do you think you had to massage the sign to make the ends meet?
     
  10. Mar 12, 2013 #9
    is it because U(x)=0
     
  11. Mar 12, 2013 #10
    Stop guessing. Get your textbook, and find out how potential energy and force are related.
     
  12. Mar 12, 2013 #11
    F=-dU/dx
    but when I put in x^2+1/4x^4 or -(-x^2-1/4^4) it is still wrong
     
  13. Mar 12, 2013 #12
    For F(x) = -2x - x^3, U(x) = x^2 + (x^4)/4 is correct. I do not know why it is not accepted. Perhaps there is some particular way you should enter it.
     
  14. Mar 12, 2013 #13
    when I input that it says ''this is not a definite integral''
     
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