Question

It is dangerous to stand close to railroad tracks when a rapidly moving commuter train passes. Explain why atmospheric pressure would push you toward the moving train.

Short answer

Rapidly moving commuter train pushes surrounding air with high velocity and creates low pressure. Then, atmospheric pressure exert force and pushes a person towards railroad tracks.

Step-by-step solution

Bernoulli’s principle

Bernoulli's principle states that an increase in kinetic energy (velocity) of the fluid decreases the pressure of the fluid and vice versa.

Low-pressure area around the train due to its speed

When the rapidly moving commuter train passes, it pushes surrounding air with high velocity. As a result of this,the kinetic energy of the air which is surrounding the train increases rapidly. According to Bernoulli's principle, this increase in kinetic energy decreases the pressure of the surrounding air. Now, atmospheric pressure acts as a high-pressure area. If the person is standing near to train, atmospheric pressure will exert force on the person and will push him/her towards the commuter train (low-pressure area) causing an accident. Hence, it is dangerous to stand close to railroad tracks when rapidly moving commuter train passes.