Simple integration for Work

[MissPenguins]

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 x_i = 6.47 m to x_f = 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

 

[Delphi51]

Agree with W = k1 x^4/4 - k2x from x1 to x2.
I got about -15000.

 

[MissPenguins]

Agree with W = k1 x^4/4 - k2x from x1 to x2.
I got about -15000.

I still didn't get that answer. :(

 

[ehild]

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

 

[MissPenguins]

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.