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0.15M3 of air is compressed from a pressure of 100kN/M2and a temperature of 20°C to apressure of 1.5MN/M2 according to the law PV1.2=CSketch this on a PV diagram (3 marks)Findi) The work done during compression.Is the work done by or on the gas?

Question

0.15M3 of air is compressed from a pressure of 100kN/M2and a temperature of 20°C to apressure of 1.5MN/M2 according to the law PV1.2=CSketch this on a PV diagram (3 marks)Findi) The work done during compression.Is the work done by or on the gas?

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Solution

To solve this problem, we need to use the work done on a gas formula for polytropic processes, which is:

W = (P2V2 - P1V1) / (1-n)

Where: P1 = Initial pressure = 100 kN/m^2 = 100,000 N/m^2 V1 = Initial volume = 0.15 m^3 P2 = Final pressure = 1.5 MN/m^2 = 1,500,000 N/m^2 n = polytropic index = 1.2

Substituting these values into the formula, we get:

W = (1,500,000 * V2 - 100,000 * 0.15) / (1 - 1.2)

We don't have the final volume (V2) given in the problem. However, we can find it using the polytropic process equation:

P1 * V1^n = P2 * V2^n

Rearranging for V2 gives:

V2 = (P1/P2)^(1/n) * V1 V2 = (100,000 / 1,500,000)^(1/1.2) * 0.15

Substitute V2 back into the work done equation to find the work done.

The work done is positive, which means work is done on the gas. This is because we are compressing the gas, which requires us to do work on it.

As for the PV diagram, it would be a curve starting from the point (V1, P1) and ending at the point (V2, P2). The curve would be concave down because the process is a polytropic compression with n > 1.

Please note that this is a text-based platform and I'm unable to sketch the diagram here. However, you can easily sketch it on a graph paper using the initial and final pressure and volume values.

This problem has been solved

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