One of the sculptures displayed on a university campus consists of a hollow cube made of six aluminum sheets, each 5 × 5 ft, welded together and reinforced with internal braces of negligible weight. The cube is mounted on a fixed base at A and can rotate freely about its vertical diagonal AB. As she passes by this display on the way to a class in mechanics, an engineering student grabs corner C of the cube and pushes it for 1.2 s in a direction perpendicular to the plane ABC with an average force of 12.5 lb. Having observed that it takes = s for the cube to complete one full revolution, she flips out her calculator and proceeds to determine the weight of the cube. What is the result of her calculation?
