Newton's Law & Gravitational F: Finding the Accl'n for a sphere

[BootyBabe]

Homework Statement

Three uniform spheres are located at the corners of an equilateral triangle. Each side of the triangle has a length of 1.20m. Two of the spheres have a mass of 2.8 kg, each.

The third sphere has an unknown mass, and is released from rest.

Considering only the gravitational forces that the spheres exert on each other, find magnitude of the initial acceleration of the third sphere.

Homework Equations

The Attempt at a Solution

I'm not sure how to attempt this question, where do I start> thanks!

 

[Doc Al]

Start with Newton's law of universal gravity.