Two fog droplets have radius 2:3 their terminal velocities are_______________?
Correct answer: B. 4:09
- A. 4:06
- B. 4:09
- C. 2:09
- D. 4.3Trying Interactive Physics Simulation Software
Explanation
For small spherical droplets in Stokes' regime, terminal velocity is proportional to the square of radius, vt ∝ r². Thus, for radii 2 units and 3 units, vt1:vt2 = 2²:3² = 4:9, so option b is correct; the likely mistake is choosing 2:9 by squaring only one radius.
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About Terminal Velocity
Terminal velocity is the constant speed reached when gravitational force is balanced by fluid resistance. The topic covers drag, buoyant force, the conditions for zero acceleration, and how viscosity, object size, shape and density affect the limiting speed, with a distinction between free fall before and after terminal velocity.
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