Why are we pulled towards a fast train moving through a station? Why do air currents make open doors shut?

Question

I'm studying for my high school physics exam, so please answer in that regard. Also, if you could explain how the answers relate that would be cool.

Answer 1

Vacuum and possible gravity, but the primary reason is air displacement as the trains especially a fast train acts like a giant fan drawing air along its path and the air that is removed must be replaced thus a vacuum is created and if you are near you can be sucked in. the same is as the door that shuts vacuum by air displacement created by movement. any teacher of physics would know the the simplest form of explanation is the best.

Answer 2

If I get your picture correctly, you are standing on a passenger deck when a train goes whizzing by. You feel a pull by wind pushing you towards the train as it speeds by.

When a body pushes fast enought through air, it pushes that air out of the way with its front end (the front of the train in your case). But as the body moves on, ambient air pressure pushes that displaced air back towards the body that displaced it. Thus, the air drafts are collapsing in toward the train in your problem. (NB: When the body is going really fast, it breaks the so-called sound barrier. At this time, the body is going so fast, the air cannot get out of the way fast enough. So there is a collision of sorts between the air and the body, which is that sonic boom we hear when a jet breaks the sound barrier.)

This is not the same physics for the closing doors. Doors do not always close, sometimes they open if they are not latched. In any case, a closing door indicates lower pressure outside than inside whatever edifice the door is on.

Most generally, the lower pressure results from something called the Bernoulli effect. Roughly, the Bernoulli effect says that air rushing at a velocity that is faster on one side of a body than on the other side will pull that body in the direction of the side with the higher velocity. In fact, it's the Bernoulli effect acting on aircraft wings that make aircraft fly because the air over the top is going faster than the air underneath its wings. Thus, the upward pull.

Clearly the velocity of wind outside a building will normally be greater than the velocity of air in a closed space. So the velocity on the outside of a door will normally be greater than on the inside of that door. Thus, the pull due to Bernoulli effect will be outward; so a partially ajar door will close.

Answer 3

i think bernoulli's principle would answer your question. try searching for bernoulli's air flow principle on google.