Two droplets each of radius 'r' are combined to form a new drop of radius 2r, theterminal speed of the new droplet is
Correct answer: B. 4Vt
- A. Vt
- B. 4Vt
- C. 9Vt
- D. 2Vt
Explanation
The terminal speed of a droplet is proportional to the square of its radius (Vt ∝ r2). When two droplets of radius 'r' combine, the volume becomes eight times greater (since the volume V ∝ r3), resulting in a new droplet with a radius of 2r. Therefore, the terminal speed increases by a factor of four (since (2r)2 = 4r2). Thus, the correct answer is 4Vt. Other options incorrectly calculate the effect of the increased radius on terminal speed.
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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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