Consider air in a piston-cylinder assembly. Initially, the air is at P1 = 2bars and T1 = 600K . The air is compressed isothermally in quasi-equilibrium to P2 = 4bars in the presence of friction between the piston and cylinder. In order to overcome friction in the compression process, a constant external pressure of P(external) = 4bars is applied to the piston.
>Take the system to be the gas in the cylinder and the piston. Show the boundary clearly on your system. In this case, do you treat friction as part of the system or surrounding?
>Take the system to be the gas in the cylinder and the piston. Find the work done on the system (gas + piston) in kJ.
>Now take the gas in the cylinder alone as your system. Find the work done on the system (gas alone) in kJ.
>What is work in kJ to overcome friction?