Question

A piston cylinder contains 0.5 kg air at 500 kpa & 500 k. The air expands in a process so pressure (p) is linearly decreasing with volume (v) to a final state of 100 kpa & 300 k. Find the work in the process?

Answer 1

Answer:

it is work on for hands and its weight is a bad news for its work

Answer 2

Thus the amount of work done is W2 = 86.1 KJ

Explanation:

P = A + BV (linear in V, decreasing means B is negative)  

From the process: 1 W2 =⌠ PdV = AREA = 1/2 (P1 + P2)(V2 - V1)

V1 = mRT1 / P1

V1 = 0.5 x 0.287 x ( 500 / 500 ) = 0.1435 m^3

V2 = mRT2 / P2

V2 = 0.5 x 0.287 x ( 300 / 100 ) = 0.4305 m^3

W2 = 1/ 2 x ( 500 + 100 ) K Pa x ( 0.4305 - 0.1435 )

W2 = 86.1 KJ

Thus the amount of work done is W2 = 86.1 KJ