MCAT Physics Question 53: Answer and Explanation

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Question: 53

8. Which of the following data sets is sufficient to determine the linear speed through an area of a rigid pipe?

  • A. The cross sectional area in another segment of pipe and the cross sectional area in the region of interest
  • B. The Reynolds number, viscosity of the fluid, density, and diameter of the pipe
  • C. The radius of the pipe, pressure gradient, viscosity, and length of the pipe
  • D. The absolute pressure and density

Correct Answer: C

Explanation:

The data given in choice (C) are sufficient to determine the flow rate through Poiseuille's law, which can then be used to determine the linear speed by dividing by the cross-sectional area (which could be determined from the radius, as well). Choice (A) would be sufficient if we also knew the flow rate in the other segment of pipe; one could use the continuity equation to determine the linear speed. The data in choice (B) could be used to determine the critical speed at which turbulent flow begins, but there is no indication that there is turbulent flow. The data in choice (D) could be used to determine the depth of an object in a fluid.

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