A piston{cylinder device containing :6 kg of Argon undergoes an isothermal trans

ID: 1860699 • Letter: A

Question

A piston{cylinder device containing :6 kg of Argon undergoes an isothermal transformation in which its

volume is doubled. If initially the Argon has a pressure of 550 kP a and a specic volume of 5

6 101 m3

kg ,

what is the nal pressure? Plot the transformation in the (V; p) plane. Assume the Ar blob is an IG.

7 The gauge pressure of an automobile tire is measured to be 190 kP a before a trip and 215 kP a after. If

the atmospheric pressure is taken to be 95 kP a and the initial temperature is 298 K, what is the nal

temperature of the air in the tire.

Assume that the tire is a rigid air blob that can be modeled as an IG: i.e. the transformation is isochoric.

Note that the pressure in the tire is the gage pressure plus the atmospheric pressure: e.g. p1 = (190 +

95) kP a = 285 kP a.

8 Combustion in a 4{stroke engine may be modeled as a constant-volume heat addition process with a xed

mass of air in the cylinder before and after combustion. Consider an engine with cylinder conditions of

1241R and 18 atm before combustion, and 3600R after it. Determine the pressure after the combustion

process.

as we know dat in an isothermal process PV = constant

ie p1v1 = p2v2

given

v2/v1 = 2

p1 = 550 kPa

putting the value we ve

P2 = v1/v2 *p1

=550/2

= 275 KPa...

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