Stokes' Law for steady motion in a fluid of infinite extent is given by:
Correct answer: A. F = 6πηrv
- A. F = 6πηrv
- B. F = (4/3)πr3ρg
- C. F = 6πηr2ρ
- D. F = 2gr2ρ/9η
Explanation
Stokes' Law describes the drag force experienced by a small spherical object moving through a fluid at a low velocity. According to the law, the drag force is proportional to the velocity of the object, the radius of the object, and the viscosity of the fluid.The formula for the drag force, F, can be written as:F = 6πηгv, Where,η is the viscosity of the fluid г is the radius of the object v is the velocity of the object
This question appeared on the UHS MDCAT 2012 paper, which you can sit online with every answer explained.
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About Fluid Drag
Fluid drag is the resistive force exerted by a liquid or gas on an object moving through it, and its value depends on speed, fluid density, shape and exposed area. Questions examine drag at low and high speeds, terminal velocity when drag balances weight, and the difference between drag and ordinary solid friction.
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