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Simple integration for Work

  • #1

Homework Statement


An applied force varies with position according to F = k1xn - k2, where n = 3, k1 = 8.3 N/m3, and k2 = 87 N. How much work is done by this force on an object that moves from xi = 6.47 m to xf = 14.9 m? Answer in units of kJ.



Homework Equations



W = k1 x4/4 ]from the integral of x1 to x2
- k2x]from x1to x2

The Attempt at a Solution


I plugged in everything, and I got 96.778 at first, then I thought I should use x33/3, then I got 6.543478 kJ.
I got both them wrong, did I do the calculation wrong? Please help, thanks. :D



SOLVED
 
Last edited:

Answers and Replies

  • #2
Delphi51
Homework Helper
3,407
10
Agree with W = k1 x^4/4 - k2x from x1 to x2.
I got about -15000.
 
  • #3
Agree with W = k1 x^4/4 - k2x from x1 to x2.
I got about -15000.
I still didn't get that answer. :(
 
  • #4
ehild
Homework Helper
15,478
1,854
It is really W = k1 x^4/4 - k2 x , and I got 97904, similar to your result. Use enough digits during the calculations.


ehild
 
  • #5
It is really W = k1 x^4/4 - k2 x , and I got 97904, similar to your result. Use enough digits during the calculations.


ehild
I found my mistake, thank you very much.
 
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