Need help with my physics homework. 1. Consider three masses that lie in the X,Y plane. The first mass, m1 lies at the origin, second mass, m2 lies at (0, Y2) and let the third mass, m3 lies at (X3, 0). Find an expression for the net gravitational acceleratoin at an arbitrary point in pace, (X,Y,Z) and show that if Z is much larger than Y2, X3, X, and Y that the acceleratoin varies approximately as Z^(-2). 2. How much work is required to dissemble the Earth. Assume that the planet is homogeneous with density p and radius R. Calculate te work required to remove shells of thickness dR from the planet and then integrate.