Have you ever been on a train going through a tunnel or plane and your ears pop?I was wondering why this happens and I know it relates to pressure but don't know exactly the reason
[Physics] Why do our ears pop
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Have you ever been on a train going through a tunnel or plane and your ears pop?I was wondering why this happens and I know it relates to pressure but don't know exactly the reason
Best Answer
When a train rushes through a tunnel, it tries to push the air out of the way, but the narrow confines of the tunnel force the air to be compressed in front of the train, as though the train were a piston in an air compressor.
The compressed air tries to find extra volume wherever it can, and since the train does not make as tight a fit to the tunnel walls as a piston, some air escapes compression by flowing between the train and the tunnel walls, eventually filling the void behind the train.
Air rushing past the train is forced into the narrow area between train and tunnel, just as though it were entering the venturi of a carburetor. So it accelerates and can flow at greater velocity than even the train's forward motion. The Bernoulli effect (http://hyperphysics.phy-astr.gsu.edu/hbase/pber.html) causes the fast-flowing air to lower the pressure between the railcars and the tunnel walls. This creates suction that draws air out of the train, effectively lowering the pressure inside the railcars.
There are two kinds of energy between the railcars and the tunnel walls: Kinetic energy of fast flowing air molecules, and kinetic energy of chaotically compressed air molecules. The laminar flow of the air is more powerful and more organized than the compression of air in the imperfectly sealed space, so the organized kinetic energy of laminar flow increases as the chaotic kinetic energy of compressed gas decreases. Energy per unit volume remains constant and conserved as air velocity increases and air pressure decreases.
Your ears pop because your eustacian tubes are trying to equalize your internal pressure fast enough to compensate for the air being sucked out of the railcars. The popping sound is air bubbles from your eustacian tube entering the middle ear.