How Do You Calculate Work Done in a Thermodynamic Process?

[Iain123]

Homework Statement

Unit mass of a fluid at a pressure of 3 bar, and with a specific volume of 0.18 m^3/kg, contained in a cylinder fitted with a piston expands reversibly to a pressure of 0.6 bar according to the law p = c/v^2
, where c is a constant. Calculate the work done during the process. (Answer = 29.82 kJ)
[/B]

Homework Equations

The Attempt at a Solution

Hi guys, its been a few years since i did any thermodynamics and I am struggling to remember how to solve this problem, iv been unsuccessfully trying to use the specific volume to get V2, and then W= P*(V2-V1).
Any help greatly appreciated ![/B]

 

[Chandra Prayaga]

Your equation for work is valid only if the pressure is constant during the process. In the process you specify, the pressure is not a constant. In such a case, the work done is obtained by integration. Are you familiar with integration?

 

[Iain123]

Ah i see, so i use this formula ?

Trying this using V1 = 0.18 and V2 = 0.9, I'm getting an answer of around 87kJ

 

[Chandra Prayaga]

In your original statement, you said the process was

p = c / v²

But in your integral, you put p = c /v.