# Thermodynamics: cylindrical figures contains a gas

1. Jan 11, 2012

### mtayab1994

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

A cylindrical figures contains a gas and we have a piston that is capable of changing the gases volume.
Initial state: V0=1l P0=10^5p T=300°K

We pressurize on the piston that has a mass m=300g and a surface S=20cm^2.
The new temperature T1=540°K

2. Relevant equations

Calculate the change in internal energy.

3. The attempt at a solution

Well I know that the change in internal energy is: ΔU=W+Q or ΔU=-P1(V1-V0)

and that p=F/S. but since my teacher didn't explain the lesson well enough I have no clue on how to answer it. Any help would be very well appreciated.

Last edited by a moderator: Jan 11, 2012
2. Jan 11, 2012

### Simon Bridge

3. Jan 11, 2012

### mtayab1994

Re: Thermodynamics

i believe i would have to use this one right?

I would get: ΔU=p1(V0-V2)+Q right?

4. Jan 11, 2012

### Simon Bridge

OK, I'll let you off the hook:
Internal energy for an ideal gas depends only on it's temperature.
$$\Delta U = \frac{3}{2}nR\Delta T$$

You know the change in temperature - it's given to you.
You need to find nR.

5. Jan 11, 2012

### mtayab1994

alright i'll give it a try right now.

6. Jan 11, 2012

### mtayab1994

I got n=.0401 by using the equation of ideal gases and i got a change of internal energy as 55J correct?

Last edited: Jan 11, 2012
7. Jan 12, 2012

### mtayab1994

Is this correct?

8. Jan 12, 2012

### Simon Bridge

I've not done the math so I cannot tell you.
But it's numbers-in-numbers-out, hard to go wrong.

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