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Water is flowing in a streamline motion through a horizontal tube. The pressure at a point in the tube is P where the velocity of now is v. At another point, where the pressure is P/2, the velocity of flow is: (density of water=ρ)

Correct answer: A. √(v2 + P/ρ)

  • A. √(v2 + P/ρ)
  • B. √(v2 - P/ρ)
  • C. √(v2 + 2P/ρ)
  • D. √(v2 - 2P/ρ)

Explanation

In a horizontal flow, Bernoulli's equation states that the sum of the pressure energy and kinetic energy per unit volume is constant. Therefore, if the pressure drops from P to P/2, the kinetic energy (and thus the velocity) must increase to conserve energy. The correct expression for velocity at the point where pressure is P/2 is derived by setting up the equation: P + 1/2 (ρv2) = P/2 + 1/2 (ρv12)Solving for v1 gives us the correct velocity: v1 = √(v2 + P/ρ).Option A correctly reflects this relationship, while the other options either overestimate or underestimate the velocity change due to pressure drop.

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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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