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A man standing near a fast moving train may fall___________?

Correct answer: C. Towards the train

  • A. On the train
  • B. Away from the train
  • C. Towards the train
  • D. On himself

Explanation

Air moves rapidly in the narrow region beside the train, so Bernoulli's principle gives lower pressure there than on the other side of the person. The greater pressure away from the train pushes the person towards it; the common mistake is choosing away from the train by assuming fast air produces greater pressure.

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About Fluid Flow

Fluid flow covers pressure, density, viscosity and the motion of liquids and gases through pipes or open channels. It includes the continuity equation, Bernoulli equation, streamline and turbulent flow, and the effects of changing area, height and speed. Viscosity and ideal fluid assumptions must not be confused with pressure effects.

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