20. A box of dimensions 1.5m x 2m x 0.8m weighs 2000N. It can rest on any of its sides. What is the largest pressure that it can exert on the floor? 21. A cylindrical concrete column is 3m high, and its diameter is 80cm. What pressure does it exert on the floor? (You'll find some relevant data in table 2.2). 22. When it was cast, the height of a concrete column was 10'. After the building above it was completed, the pressure on that column was 30,000 pounds per square inch (psi). By how much did the column contract due to that pressure? CL F 23. A brick of base area 4"x8"is cemented by concrete to the floor. What horizontal force F is needed in order to break the concrete? Assume that both the brick and the bonding between the brick and the concrete are stronger than the concrete. 24. A steel pipe, 12' long, of inside diameter 2" and outside diameter 2.2" is filled with concrete, and then used as a column in a structure. It carries a load of 10,000 pounds. By how much did it contract because of that load? Ignore lateral deformations of the column.