Question

The maximum weight M that can be supported by a beam is jointly proportional to its width w in inches and the square of its height h in inches and inversely proportional to its length L in feet. (a) Write an equation that expresses this proportionality. (Use k as the constant of proportionality.) (b) Determine the constant of proportionality if a beam 4 in. wide, 6 in. high, and 15 ft long can support a weight of 3840 lb. k

Answer 1

M = kwh^2/L

k = 400

Explanation:

Given that the maximum weight M that can be supported by a beam is jointly proportional to its width w in inches and the square of its height h in inches and inversely proportional to its length L in feet

Then

M ∝ wh^2/L

M = kwh^2/L

where k is the constant of proportionality

if a beam 4 in. wide, 6 in. high, and 15 ft long can support a weight of 3840 lb then

3840 = k * 4 * 6^2/15

k = 3840 * 15 / (4 * 36)

k = 400