Bernoulli Effect The Bernoulli effect describes the fact that the pressure increases as air (indeed any gas and fluid) flows at higher velocity. Thus high velocity air has a low pressure and low velocity air (or air at-rest) has higher pressure. Notes on the Bernoulli effect and the New Brunswick to New York Train Ride. By Mark Croft 1.) The main New Brunswick (NB) train station is on the on the NY bound side of the tracks. In addition to the NJ-to-NY commuter trains, that stop in NB, there are also AMTRACK Washington-to-NY trains that go zipping through the station. When a train speeds through the station it drags air along with it, as is well known to anyone who has ever felt the accompanying blast of the wind on the train platform. If you are ever in the NB train station at such a time, you should note that the terminal doors (adjacent to the track) swing outward. They do so by virtue of the Bernoulli effect. The passing train causes air to flow past the outside of the doors, which, by the Bernoulli effect, induces a low pressure compared to the still-air in the station. The pressure difference draws air out of the station and the doors swing out. Extending this effect to the much higher wind velocities in a tornado seems to explain a couple of things I have heard over the years. For example, the large inside- still-air/outside-high-speed-air pressure difference makes the reports of houses sometimes "exploding" in a tornado seem plausible. It also appears to explain the precaution of opening windows/doors when a tornado approaches. I should say that these observations are "hear say" for me and any confirming or discrediting information would be welcome. 2.) When taking a train into NY-Penn. Station one passes through the NJ- Meadowlands and thence into a tunnel. When entering this tunnel, there is a pressure change in the in the train perceptible by a pressure change on your eardrums. Here the walls of the tunnel place a drag on the air being pulled along by the train. The speed of the air next to the train increases, the pressure drops, air is pulled out of the train and the pressure inside decreases. 3.) The physics in the above two observations is essentially equivalent if considered from a transformation of reference frames view point. To paraphrase Einstein on this; "the laws of physics must be the same as viewed from any inertial (constant relative velocity) reference frame". In the terminal (or looking out a service entrance in the wall of the tunnel) we see the train rushing past with velocity v. On the train we see the terminal/tunnel rushing past at a velocity –v. From both reference frames one sees a surface rushing past dragging air with it and hence both observe a similar pressure drop.