STEM与日常科技·英语30篇（3）
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Bernoulli’s Principle and the Safety Line at Train Platforms
伯努利原理与地铁站台安全线的科学依据
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When a fast train passes a platform, air between the train and passenger moves faster than surrounding air.
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According to Bernoulli’s principle, faster-moving air exerts lower pressure than slower-moving air.
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This pressure difference creates a subtle but real inward force pulling objects toward the moving train.
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That’s why standing too close feels unnerving—and why platforms mark safety lines clearly.
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The effect is stronger with higher speeds, wider trains, and tighter platform gaps.
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Even bicycles or loose coats can be tugged dangerously if someone leans past the line.
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Ventilation systems in underground stations must account for this airflow disturbance during peak hours.
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Some newer platforms install platform screen doors partly to eliminate this aerodynamic risk entirely.
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Similar physics explains why airplanes lift off and why shower curtains billow inward during hot showers.
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Safety lines exist not just as warnings—but as visible boundaries against invisible forces.