Final answer:
Standing near railroad tracks is dangerous when a train passes by due to Bernoulli's principle, which causes a pressure difference that can push you toward the train.
Step-by-step explanation:
It is dangerous to stand close to railroad tracks when a rapidly moving commuter train passes because of a phenomenon that is explained by Bernoulli's principle.
As a train speeds by, it causes the air around it to move rapidly as well. According to Bernoulli's principle, an increase in the velocity of a fluid, which in this case is air, leads to a drop in pressure.
The side of your body facing the train experiences this lower pressure, while the other side of your body is still subject to normal atmospheric pressure.
The difference in pressure pushes you toward the train, making it hazardous to stand too close to railroad tracks when a train is passing at high speed.