# Work done by stretching a STring

1. Apr 11, 2008

### nickclarson

I have been looking all over for an equation to find the work done on a steel string that is stretched L meters.

"Find the work needed to stretch the string."

I know it has variable forces so I was thinking I could use elastic potential

$$U=\frac{kx^{2}}_{2}$$

but now I have the problem finding out what K is.

ANY help is appreciated thanks.

Nick

2. Apr 11, 2008

### Dick

Is this a homework problem? That can't be the full question. You've got the right idea if the steel wire can be considered as a spring. You'll need a modulus of elasticity and the geometry of the wire to actually do this.

3. Apr 11, 2008

### nickclarson

yea I have the area of the wire and the modulus... I just need help figuring out which equation to use.

Thanks,
Nick

4. Apr 11, 2008

### Dick

Didn't they give you a formula for that as well? The elastic modulus Y, has units of N/m^2, yes? k should have units of N/m. So I would guess on purely dimensional grounds that if L is length and A is cross sectional area that k=Y*A/L. Can you confirm that by doing some research? Units are your friend. Exploit them.