Eight spherical rain drops of same mass and radius are falling with terminal velocity 6 cm/s. If they combine to form one big drop, what is its terminal speed?
Correct answer: C. 24 cm/s
- A. 1.5 cm/s
- B. 6 cm/s
- C. 24 cm/s
- D. 32 cm/s
Explanation
Combining 8 equal drops doubles the radius (since volume ∝ r³). Terminal velocity scales ∝ r², so new velocity = 4×6 = 24 cm/s.
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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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