Problem with ideal gas law and a spring! Help please

1. Apr 11, 2007

ml_lulu

Problem with ideal gas law and a spring! Help please!!

1. The problem statement, all variables and given/known data

We have a box divided in two parts by a piston without friction, and in one part there are n moles of an ideal gas and a Spring orf constant K and natural longitude L which keeps the piston in equilibrium. According to this, and knowing that the temperature of the gas is T0, find the amount for K.

2. Relevant equations

PV=nRT
F=-KX
E=(KX^2)/2

3. The attempt at a solution

2. Apr 11, 2007

denverdoc

what do you know besides eqn. How do we link the two systems?

The common part to both is the piston, so Pressure of the gas multiplied by its area exerts a force on it.

This force must be the same as that exerted by the spring in order for system to be in equilibrium, that is piston is not moving.

Does this help?

3. Apr 11, 2007

ml_lulu

I forgot to tell that the longitude of the spring in equilibrium is 3L (which means that x=2L, I think?) So, what I did is:

P= F/A
F=-kX
PV=nRT

kX/A=nRT/V

And volume is one, because its an ideal gas, so

K=nRTA/X

K=nRTA/2L

And thats all I know

4. Apr 11, 2007

ml_lulu

Forget it! I did it :rofl: :tongue2:

F/A*V=nRT
F*L=nRT
kX*L=nRT
K=nRT/X.L
K=nRT/2L*3L
K=nRT/6L^2

Thanks anyways!! :)

5. Apr 11, 2007

denverdoc

Thanks, I was wondering where the 6 came from

Thats getting real close,