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Stokes' law applies to very small, slow-moving objects in a dense fluid, such as bacteria settling in water. How does the drag force in Stokes' law depend on the object's speed?
AIt does not depend on the object's speed at all
BIt is proportional to the square of the speed
CIt is proportional to the speed itself, not its square
DIt is proportional to the speed cubed, not just the speed
Answer & Solution
Correct answer: C. It is proportional to the speed itself, not its square
1. The quadratic drag law discussed earlier only holds for larger objects moving at ordinary speeds.
2. For very small or very slow objects, or objects in a denser medium, that quadratic law breaks down.
3. In that regime, the drag force becomes proportional just to the velocity, which is Stokes' law.
4. This is a direct, first-power dependence on speed, not a square or cube dependence, and not independence from speed.
_Source: OpenStax College Physics (CC BY 4.0), Ch 5 "Further Applications of Newton's Laws: Friction, Drag, and Elasticity", section 5.2 Drag Forces_
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