I know how to find the center of mass of a 2 dimensional object like a piece of plywood or something like that, but when it comes to 3-D objects i'm clueless. All I know is Mx=x1m1+x2m2+...xnmn here is my problem, i don't know if i should split the pyramid into 4ths or not. The Great Pyramid of Cheops at El Gizeh, Egypt, had a height H = 144.9 m before its topmost stone fell. Its base is a square with edge length L = 233 m. Its volume V is equal L2H/3. Assuming that it has uniform density p(rho) = 1.8 x 103 kg/m3. (a) What is the original height of its center of mass above the base? (b) What is the work required to lift all the blocks into place from the base level?