Question

Operators operating trains in the subway or open cuts are forbidden to pass a location where water has accumulated to the ball of the running rail. The depth of water over the ties at such time is closest to _____ inches?

Answer 1

When a train moves past a person at high speed, the displacement of air can create a low-pressure area that might cause the person to be drawn towards the train. The exact permissible depth of water over railroad ties was not given in the context; this would depend on specific railroad safety regulations.

Step-by-step explanation:

The danger of standing close to railroad tracks as a rapidly moving commuter train passes is linked to the phenomenon of atmospheric pressure changes. When a train moves swiftly past, it displaces the air around it, creating a low-pressure area near the train. This pressure difference can cause a person standing by the track to be drawn towards the train due to higher atmospheric pressure on their other side, pushing them into the low-pressure zone by the train. This is a simple illustration of Bernoulli's principle, where higher velocity fluids (including air) generate lower pressure.

To answer the question about the permissible depth of water over the railroad ties, it would be the depth that does not exceed the ball of the rail. Unfortunately, the exact measurement in inches was not provided within the given context. This would require specific safety regulations which dictate the maximum permissible water depth for safe train operation.