Consider an open container at standard atmospheric pressure. Now a lid is placed over it, in the most normal way possible. Would the pressure of gas inside the container be the same as the standard atmospheric pressure? If not would it nearly be the same? What changes can covering with a lid cause?

My argument is that the pressure would depend on whether there was any compression or not while covering. Is there any compression?

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    $\begingroup$ If you slammed the lid down fast enough you'd increase the pressure in the container because the motion of the lid would generate a pressure wave at its leading edge. Beyond that I'm not sure we can comment. $\endgroup$ – John Rennie Jan 27 '15 at 18:00

This reminds me of Galileo's famous gedankenexperiment: what happens to a body in motion if the friction of a surface becomes less and less until it goes to zero?

If you put the lid on infinitely careful and slowly, and there are no heating sources in or outside the pan, there will not be compression and the pressure will be the same throughout.


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