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**fogel1497** Question: If the work required to stretch a spring 1 ft beyond its natural length is 9 ft-lb, how much work *W* is needed to stretch it 10 in. beyond its natural length?

So my teacher today gave us some physics equations and said to do this homework. Im a little stuck on this, usually they give us the force required to stretch a spring, not the work. Here is what i tried:

W=FD

so

9=F*1ft

F=9

Then I did F=KX (hooke's law) to solve for the k constant of the spring

so

9 = K * 1 ft

K = 9

So I now know that F = 9X (equation for force of a spring when you know the k constant of that spring)

And then i said the:

INTEGRAL of: 9x from 0-10/12 = Total work needed to stretch the spring 10inches.

I get 7.25, but this answer is wrong.