An object having spherical shape of radius 'r' experiences a retarding force F from a fluid of coefficient of viscosity 'η' when moving through the fluid with speed 'v'. What is the ratio of retarding force to speed?
Correct answer: C. 6πη r
- A. 6πη r2
- B. 6πη/r2
- C. 6πη r
- D. 6πη/r
Explanation
Retarding force=6πη r v. ratio of retarding force to speed (v) would be (6πη r v)/v which equals 6πη r.
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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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