Perplexing Thermodynamics problem.Help!

  • Thread starter kilroymcb
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  • #1

Main Question or Discussion Point

This problem has been puzzling me and several classmates for days now. The answer is due monday. I need some help.

"An air pistol contains compressed air in a small cylinder. Assume that the volume is 1 cm^3, pressure is 1 Mpa and the temperature is 27 C when released, the air expands in an isothermal process. If the air pressure is .1 Mpa in the cylinder as the bullet leaves the gun, find A) the final volume and the mass of air B) the work done by the air and the work done on the atmosphere C) the work to the bullet and the bullet exit velocity.

I have no problem with part A, but part B and C pose the problem. Since the mass of the bullet is not given, how can you calculate the work done to the bullet and the bullet exit velocity? I dont even know where to begin.


Answers and Replies

  • #2
Just integrate W = integral P dV for V1 to V2 (which you know both) isohermal expansin PoVo is constant (isentropic expansion is probably more realistic.