Compression of a Jaguar XK8 Cylinder

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SUMMARY

The discussion focuses on the compression of air in a Jaguar XK8's eight-cylinder engine during the compression stroke. Initially, the cylinder contains 499 cm³ of air at atmospheric pressure (1.01 x 10^5 Pa) and a temperature of 27.0 degrees Celsius. After compression to a volume of 46.2 cm³, the gauge pressure increases to 2.72 x 10^6 Pa. The correct calculation for the final temperature, using the ideal gas law, results in a temperature of 503 degrees Celsius.

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  • Understanding of the Ideal Gas Law
  • Knowledge of gauge and absolute pressure concepts
  • Ability to convert between units of volume (cm³ to m³)
  • Familiarity with temperature conversion from Celsius to Kelvin
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  • Learn about gauge pressure and how it relates to absolute pressure
  • Practice unit conversions, particularly for volume and temperature
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Homework Statement


A Jaguar XK8 convertible has an eight-cylinder engine. At the beginning of its compression stroke, one of the cylinders contains 499 cm^3 of air at atmospheric pressure (1.01 x 10^5 Pa) and a temperature of 27.0 degrees celsius. At the end of the stroke, the air has been compressed to a volume of 46.2 cm^3 and the gauge pressure has increased to 2.72 x 10^6 Pa.


Homework Equations


(p1)(V1)/T1 = (p2)(V2)/T2
where p = pressure, V = volume, T = temperature


The Attempt at a Solution


What I tried was:
((1.01 x 10^5)(0.0499))/300 = ((2.72 x 10^6)(4.62 x 10^-4))/T2

I converted the 499cm cubed and the 46.2cm cubed to meters cubed, and also for T1 I did 273(kelvins) + 27

There was a hint given that the 'gauge pressure is the difference between the absolute pressure and the atmospheric pressure. Thus, if you measure a gauge pressure pg, then the absolute pressure p is given by p= pa + pg, where pa is the atmospheric pressure.' So I was thinking for p2 to use ((1.01 x 10^5)+(2.72 x 10^6)) but still did not get the right answer.

The answer to this question is 503 degrees Celsius but I just can't figure out what number to use for p2.
 
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You don't have to convert the cm^3 to m^3. If they are both in the same units, just use them as they are. The units will cancel out. The pressure goes up by a factor of about 20 and the volume drops by a factor of about 10. The temperature should about double. You are making a mistake in converting the volumes. 499cm^3=4.99*10^(-4)m^3. 46.2cm^3=4.62*10^(-5)m^3. And, yes, use the gauge pressure thing to make fine adjustments.
 
Last edited:
Oh okay thank you for the clarification! I was able to get the answer :)
 

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