Serway & Jewett — Linear Momentum and Collisions: Problem 25

Explorers in the jungle find an ancient monument in the shape of a large isosceles triangle as shown in Figure P9.25. The monument is made from tens of thousands of small stone blocks of density \(3\,800\text{ kg/m}^3\). The monument is \(15.7\text{ m}\) high and \(64.8\text{ m}\) wide at its base and is everywhere \(3.60\text{ m}\) thick from front to back. Before the monument was built many years ago, all the stone blocks lay on the ground. How much work did laborers do on the blocks to put them in position while building the entire monument? Note: The gravitational potential energy of an object–Earth system is given by \(U_g = Mgy_{CM}\), where \(M\) is the total mass of the object and \(y_{CM}\) is the elevation of its center of mass above the chosen reference level.