# Potential Energy HW problem - Help

1. Feb 15, 2010

### woo

1. The problem statement, all variables and given/known data
So this is my first post and, I've been working on this problem for a while and am having trouble wrapping my head around it... I tried searching but couldn't find anything that helped..
So here's the problem.

In one dimension, the magnitude of the gravitational force of attraction between a particle of mass M1, and one of mass M2 is given by:
Fx(x)=GM1M2/x2
Where G is a constant and x is the distance between the particles.

a) What is the potential energy function U(x)? Assume that U(x) -> 0 as x -> infinity.
b) How much work is required to increase the separation of the particles from x=x1 to x=x1+d?

2. Relevant equations

-dU(x)/dx=Fx(x)

3. The attempt at a solution
The solution given in the book is..a) U(x)=-Gm1m2/x
b) Gm1m2d/x1(x1+d)

Here is what I've been trying..
-dU(x)/dx=Gx1x2/x2

U(x)-U(x0)=-$$\int$$(Gm1m2/x2)dx

Last edited: Feb 15, 2010
2. Feb 15, 2010

### flatmaster

Yep. Now simply do the integral. And apply your boundry condition U(inf) = 0