An object moving through a fluid experiences a retarding force known as drag force. The drag force as the speed of the object:
Correct answer: D. Increases ... Increases
- A. Decreases ... Decreases
- B. Decreases ... Increases
- C. Increases ... Decreases
- D. Increases ... Increases
Explanation
For small objects (such as a bacterium) moving in a denser medium (such as water), the drag force is given by Stokes' law, Fs=6πηrv F s = 6 π η r v , where r is the radius of the object, η is the fluid viscosity, and v is the object's velocity.Drag force is directly proportional to the velocity of the object. So, when the velocity of the object increases, the drag force also increases. A is not always the case for drag force.
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About Fluid Dynamics
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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