The maximum safe load of a rectangle beam varies jointly as its width and the square of its depth and inversely as the length of the beam. If a beam 8.00 in. wide, 11.5 in. Deep, and 16.0 ft long can safely support 15.000 lb, find the safe load for a beam 6.50 in. Wide, 13.4 in. Deep, and 21.0 ft long made of the same material.

Answer 1

x = k *w*d^2/L

15,000 = k *8*11.5^2/16
so
k = 226.8

x = 226.8 * 6.5 * 13.4^2 / 21
= 12,608 pounds