In order to measure the energy of projectiles, a test facility consisting of a horizontal insulated tube, closed at one end and with a frictionless piston of mass 1.5 kg at the other is used. The tube has a cross sectional area of 0.05 m2 and contains 1.15 kg of air at 20 °C and 100 kPa. During a test the piston is struck by a bullet of mass 0.15 kg travelling at 800 m/s, which remains embedded in the piston. It rapidly moves and compresses the air bringing the piston and bullet to rest.(adsbygoogle = window.adsbygoogle || []).push({});

For air R = 0.287 kJ kg–1 K–1 ; Cp = 1.005 kJ kg–1 K–1 .

Assuming the bullet is embedded in the piston, and momentum is conserved, and reversible adiabatic compression of the air in the tube, calculate the temperature of air at the end of compression when the piston has stopped.

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P1 = 100 kPa; T1 = 293K and so using PV=mRT, I calculated V1 to be 0.967 (3dp) and so the length of the chamber would be the V/A => 19.34m and if I was given the length it was compressed to (or if someone could kindly point out how to calculate it) I could work out T2 using T2 = T1 (V1/V2)^k-1 as it's adiabatic.

Any help would be really appreciated!

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# Homework Help: Could this question be calculated without knowing the change in length?

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