Moderate

When will liquid flow in a pipe be most smooth (streamline)?

Correct answer: B. High thickness & low density in small pipe

  • A. High thickness & high density in small pipe
  • B. High thickness & low density in small pipe
  • C. Low thickness & low density in large pipe
  • D. Low thickness & high density in large pipe

Explanation

Laminar flow occurs at low Reynolds number, Re= ρvD/μ. High viscosity (large μ) and small pipe diameter D reduce Re; lower fluid density ρ also helps. Thus, high viscosity + low density in a small pipe promotes streamlined (laminar) flow.

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Fluid flow is described through speed, pressure and density, including steady flow and the equation of continuity for conserving mass. Bernoulli's equation relates pressure, speed and height, while fluid drag and terminal velocity explain why a falling object eventually moves at constant speed when drag balances its weight.

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