Answer:
Explanation:
Given
Force [tex]F=4\ lb[/tex]
extension [tex]x=1\ ft[/tex]
And Force [tex]F=kx[/tex]
where k=spring constant
[tex]k=\frac{F}{x}=\frac{4}{1}=4\ lb/ft[/tex]
Work done require to stretch the spring to 4 ft beyond its natural length
[tex]W=\int_{0}^{4}Fdx[/tex]
[tex]W=\int_{0}^{4}4xdx[/tex]
[tex]W=\left [ 2x^2\right ]^{4}_{0}[/tex]
[tex]W=2\times 6^2=32\ lb-ft[/tex]
