Why can two streamlines in a steady flow never cross each other?
Correct answer B. A fluid particle at the crossing point would have two velocities at once
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Fluid Dynamics MCQs
Page 2 of Fluid Dynamics multiple-choice questions with answers. Tap an option to check yourself.
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Which statement correctly describes steady (streamline) flow of a fluid?
Correct answer B. The velocity of the fluid at any given point does not change with time
A skydiver falling at terminal velocity changes from a spread-eagle position to a head-down position. What happens to her terminal velocity?
Correct answer B. It increases because the drag at any given speed is reduced
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A falling ball of mass 0.050 kg has reached its terminal velocity in air. Ignoring upthrust, what is the drag force acting on it (g = 9.8 m/s²)?
Correct answer B. 0.49 N
A glass sphere of radius 1.0 mm and density 2500 kg/m³ falls through glycerine of density 1260 kg/m³ and viscosity 1.5 Pa s. What is its terminal velocity (g = 9.8 m/s²)?
Correct answer D. 1.8 mm/s
A dust particle of radius 1.0 × 10⁻⁵ m moves at 0.50 m/s through air of viscosity 1.8 × 10⁻⁵ Pa s. What is the Stokes drag force on it?
Correct answer C. 1.7 × 10⁻⁹ N
A tiny oil droplet falls through air with a terminal velocity of 2.0 mm/s. What is the terminal velocity of a similar droplet of three times the radius?
Correct answer A. 18 mm/s
For a small sphere falling through a viscous fluid, how does its terminal velocity depend on its radius r?
Correct answer D. It is proportional to r²
A small steel ball falling through a viscous liquid reaches its terminal velocity when ____.
Correct answer A. the net force on it becomes zero
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Which quantity does NOT appear in Stokes’ law for the drag force on a sphere moving slowly through a fluid?
Correct answer B. Density of the sphere