Question

2. The work done by substance in a reversible non-flow manner in accordance with V=700/P where V is

volume in m 3 , P is absolute pressure in Kpaa. Evaluate the work done on or by the substance as the

pressure increases from 85 to 810 KPa

Answer 1

$W = \int PdV \\ V= \frac{700}{P} \\ W = (-\frac{700}{P^2})dP \\ W = \int P(\frac{-700}{P^2}dP$

$W = -700 \int \frac{dP}{P}$ from 85 to 810 kPa

$W = -700(ln(810) -ln(85)) \\ W = -700ln(\frac{810}{85}) = -700ln(9.529) \\ W = -700 \times 2.254 = -1577.8 \;kN-m$