1. The problem statement, all variables and given/known data 1kg of helium in a closed system has 40kj added by heating & 100kj removed by work during a reversible polytropic process. The initial temp of the gas is 300K & the initial pressure is 100kN/m2 Q. find the final temp of the gas & pressure 2. Relevant equations given: Cp=14.57 kgK & M=4 3. The attempt at a solution Hi guys, I can't get my head around how to work out the final pressure (P2) I got the Temp correct (T2) bu doing the following: R=Ru/M R =2.0785 Cv = R +Cp Cv = 7.2715 closed system so V= const Qnet = -100 -40 =-140 qnet = Q/m qnet = Cv(T2-T1) T2 = 281K Can't think how to work out P2 when I dont have n any help?