Question

A weight of 18,000 lb is supported on a rectangular base plate that is 9 in. wide and 2 ft long. the base plate rests on a concrete slab. determine the stress that the base plate exerts on the concrete slab. express your answer in units of (a) lb/in.2 and (b) lb/ft2. (precision of 1 for (a) and of 1000 for (b))

Answer 1

We want to find the area of the plate in square inches and square feet.  
1) Here we need inches. The area is 9in * 24in =216 in.^2., since 1ft = 12in. 18,000lb / 216 in.^2 = 83lb/in.^2  
2) Here we need feet. With 12 in = 1 ft, 9in = .75ft. The area is .75ft * 2ft = 1.5 ft.^2 
18,000lb / 1.5 ft.^2 = 12,000lb/ft.^2