# Homework Help: Pressure from compression

1. Jun 3, 2010

### ghostbuster25

a sample of an idel monotomic gas is intially at a pressure 1.6*10^4Pa and undergoes an adiabatic compression which halves the volume. What is the final pressure?

ive been trying to find a way of useing the equation W=-P$$\Delta$$V but am starting to think this is the wrong one as i cant see how i can use it.

any suggestions?

2. Jun 3, 2010

### ehild

Find the relation between pressure and volume of an ideal gas during an adiabatic process.

ehild

3. Jun 3, 2010

### ghostbuster25

sorry i cant see it :(,

i can only see that p*V= a constant but not sure how to use that here!

am i way off track?

4. Jun 3, 2010

5. Jun 3, 2010

### ghostbuster25

im still unclear on the relationship after reading that

6. Jun 3, 2010

### rock.freak667

Last edited by a moderator: Apr 25, 2017
7. Jun 3, 2010

### ehild

The mathematical equation for an ideal fluid undergoing a reversible (i.e., no entropy generation) adiabatic process is

$$P V^{\gamma} = \operatorname{constant} \qquad$$

where P is pressure, V is volume, and

$$\gamma = {C_{P} \over C_{V}} = \frac{\alpha + 1}{\alpha}$$,

CP being the specific heat for constant pressure, CV being the specific heat for constant volume, γ is the adiabatic index, and α is the number of degrees of freedom divided by 2 (3/2 for monatomic gas, 5/2 for diatomic gas).

ehild