Zephyra is standing on a train platform holding a helium-filled balloon on a string. As a train rapidly passes by her, but not stopping at the station, in what direction will the balloon move? Respond very briefly.
The balloon will move towards the train as it passes. When the train moves quickly, it creates a low-pressure area immediately next to it because it is pushing air out of the way as it speeds by. The higher pressure air from the platform pushes the lighter helium balloon toward the low-pressure area, causing the balloon to move towards the train. This is an example of Bernoulli's principle, where an increase in the speed of the air or fluid results in a decrease in pressure.