# Gravitaional Potential Energy help, please

1. Nov 20, 2012

### chemEcook

1. The problem statement, all variables and given/known data
Four uniform spheres, with masses mA = 350 kg, mB = 600 kg, mC = 1500 kg, and mD = 300 kg, have (x, y) coordinates of (0, 50 cm), (0, 0), (-80 cm, 0), and (40 cm, 0), respectively. Sphere A is then removed.
(a) Calculate the gravitational potential energy of the remaining three-particle system.

2. Relevant equations
U=-Gm1m2/r12-Gm1m3/r13-...

3. The attempt at a solution
U=-G(McMd/Rcd+McMb/Rcb+MbMd/Rbd)
U=-G(1500*300/.12+1500*600/.8+600*300/.4)=-3.55e-4 J
It's telling me this is wrong but I can't see where I'm going wrong. Thanks in advance.

Last edited: Nov 20, 2012
2. Nov 20, 2012

### chemEcook

Nevermind. I found my small error. Thanks, anyway.