# Homework Help: An applied force varies with position

1. Nov 11, 2012

### SonRuy

An applied force varies with position according to F = k1 xn− k2, where n = 3,
k1 = 2.4 N/m3, and k2 = 56 N.
How much work is done by this force on an object that moves from xi = 5.13 m to xf = 28.2 m?

i keep using the integration equation: w = ∫f(x) dx
where k1x^4/4 - 56x is the new equation which i plug 28.2m and 5.13m and subtract
i get 377736.527

2. Nov 11, 2012

### Staff: Mentor

I haven't checked your arithmetic, but you're attacking the problem in the right way. What's the correct answer that you aren't getting?

3. Nov 12, 2012

### ehild

What is the unit of your result? You need to give the result in units of kJ.

ehild

4. Nov 12, 2012

### Basic_Physics

5. Nov 12, 2012

### haruspex

No, I also get 377736; but that's J, so the answer should be 377.7kJ.

6. Nov 13, 2012

### ehild

That is the correct result. Maybe it should be rounded to three digits: 378 kJ.

ehild

7. Nov 13, 2012

### Basic_Physics

Ok. Left the /4 out.