Moderate

Water is moving with a speed of 5.18 ms-1 through a pipe with a cross- sectional area of 4.20 cm3 The water gradually descends 9.66 m as the pipe increase in area to 7.60 cm3 The speed of flow at the lower level is:

Correct answer: D. 2.86 ms-1

  • A. 3.0 ms-1
  • B. 3.82 ms-1
  • C. 5.7 ms-1
  • D. 2.86 ms-1

Explanation

The correct answer is Option D:2.86 ms-1. To find the speed at the lower level, use the continuity equation: A1V1 = A2V2 where A1 and V1 are the initial area and speed, and A2 and V2 are the area and speed at the lower level. Given A1 = 4.20 cm3, V1 = 5.18 ms-1, and A2 = 7.60 cm3, solve for V2: V1 = (A1 * V1) / A2 = (4.20 * 5.18) / 7.60 = 2.86 ms-1.

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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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