Question

The stress distribution on a structure is given by s=2x^2+4x−30 where s is stress in pounds per square inch and x is the distance in feet from a reference point. At what distance is the stress equal to 0?

f)6 ft g)3 ft h)12 ft j)5 ft

Answer 1

Explanation:

Set the stress function s(x) = 2x^2 + 4x - 30 equal to zero and solve the resulting equation for x:

s(x) = 2x^2 + 4x - 30, or (after reduction), s(x)/2 = x^2 + 2x - 15 = 0.

Solve this by factoring: (x - 5)(x + 3) = 0 yields x: {-3, 5}

Assuming that x is positive (all distances are positive), x = 5

Answer j is correct: x = 5 ft; at x = 5 ft, the stress will be zero at x = 5 ft.