# Gas pressure force

1. Sep 15, 2005

### ice87

A cubic metal box with sides of length 20cm contains air at pressure of 1atm and a temperature of 300K. The box is sealed so that the volume is constant and heated to 400K. What is the net force on each side of the box?

thanks dudes.

2. Sep 16, 2005

### Pengwuino

Use PV=nRT

3. Sep 16, 2005

### Tom Mattson

Staff Emeritus
You'll also need the definition of pressure. It's a force divided by an area.

4. Sep 16, 2005

### SpaceTiger

Staff Emeritus
Yes, this is related to the ideal gas law (Pengwuino's formula), but really, all you need to know is the proportionality:

$$\frac{P_2}{P_1}=\frac{T_2}{T_1}$$

To see why, consider that both before and after the gas is heated, it must satisfy the ideal gas law. Now, look at which variables are the same both before and after. Does the volume change? What about the number of particles in the box? Certainly the gas constant isn't going to change.

Once you determine the pressure, do you know the relationship between pressure and force?