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mathnoobie
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Homework Statement
Use Hooke's Law to determine the variable force in spring problem.
Eighteen foot-pounds of work is required to stretch a spring 4 inches from it's natural length. Find the work required to stretch the spring an additional 3 inches.
Homework Equations
W=∫f(x)dx
f=kd
The Attempt at a Solution
I set the work equal to 18 and the distance equal to 4.
so 18=4K, K=18/4
with this knowledge I set my function is (18/4)X
integrating
∫(18x/4)dx from 4 to 7
I get 9x(^2)/4
using the fundamental theorum of Calculus from 4 to 7
I get 74 1/4 (not sure of units, is it inches-pound)