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Im not exactly sure myself, But if i was to follow the equation. if work is done on system, q= u - w u =82.11 w=109.40 do advise. thanks! its a typo. its 82.11, not 89.11. sorry

thanks for the reply! v2=158*10^-6 / 5.3 = 29.81 * 10^-6 m3 Using Pv=mrt to find mass mass= 0.00058141kg T2= T1(p2/p1)^0.3/1.3 = 499.7k Delta U = 0.00058141 * ( 1.005-0.287)(1000) (499.97-303)=82.11J SInce work is added in the system for compression U=Q+w Q=U-W q= 82.11 - p2v2-p1v1/n-1 = 89.11-109.40=-0.027KJ (ANS)

Hi guys, The question is: Initially a piston cylinder contains air at p1=3.2bar (absolute) and the contained volume is v1=158m3 at temperatuer t1=303k. The air is then compressed, with compression ratio r=v1/v2=5.3. the polytropic index of compression is n=1.3 estimate the net heat addition in KJ. With p2 found in my working, do i need to add my p2+p1 ? Thanks