Calculating Work to Compression a Spring 4.08cm with 718N Force"

[kdizzle711]

To stretch a spring a distance 3.09cm from its unstretched length, an amount of work of11.1j must be done. How much work must be done to compress this spring a distance 4.08 from its unstretched length?

I have been using the equation
k=Fx/x
W=(1/2)kx2^2-(1/2)kx1^2

11.1=(1/2)(Fx/.0309)*(.0309^2)-(0)
Fx=718N

So I plug 718N into
W=(1/2)(718/.0408)*(.0408^2)
I get 14.6 but it is still not the right answer someone please help

 

[PhanthomJay]

You've put in an unneeded extra step here in solving for F, and in so doing, you have made in error in your last equation. If you solved that k = 718/.0309 in the first step, why are you using k=718/.0408 in the other? The k must be the same.

 

[Doc Al]

I have been using the equation
k=Fx/x

You won't need this, since you don't care about the force.

W=(1/2)kx2^2-(1/2)kx1^2

You'll need this.

First step: Use the data for the 3.09 cm stretch to find k.

 

[kdizzle711]

Thank you, I didnt even notice that