Use the PV diagram of a system. The units for P and V are atmospheric pressure atm and liter L. Process A to B and B to C are straight lines on it.

Question

How much is the work done by the system from A to C in J?

Given these coordinates:(volume on the x, pressure on the y)
A: (1 Li, 3.0 atm)
B: (5 Li, 6.0 atm)
C: (11 Li, 4.5 atm)

Answer 1

A: p₁=3 atm =3.04•10⁵ Pa,
V₁=1 L = 10⁻³ m³;
B: p₂=6 atm = 6.08•10⁵ Pa,
V₂ =5L=5•10⁻³m³;
C: p₃= 4.5 atm = 4.56•10⁵ Pa,
V₃=11L = 11•10⁻³m³.

A->B:
W₁= 0.5(p₁+p₂)( V₂-V₁) =
=0.5(3.04+6.08)•10⁵•(5-1)•10⁻³ =
=1824 J
B->C:
W₂ =0.5(p₂ +p₃)( V₃-V₂) =
=0.5( 6.08+4.56)•10⁵•(11-5)•10⁻³ =
=3192 J

W= W₁+W₂ =1824 + 3192 =5016 J