A small spherical droplet of density d floats exactly half immersed in a liquid of density ρ and surface tension T. Surface tension provides an upward force. Find the droplet radius.
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A small spherical droplet of density d floats exactly half immersed in a liquid of density ρ and surface tension T. Surface tension provides an upward force. Find the droplet radius.

G1 Physics · Accepted Answer

Step 1: Use surface-energy/pressure relations: ΔP = 2T/R for a liquid drop or 4T/R for a soap bubble, capillary rise h = 2T cosθ/(ρgr), and surface energy = TΔA. Step 2: Apply force or energy balance to the stated radii and surface areas. Applying these relations to the given data gives B: √[3T/{(2d−ρ)g}]. Final answer: B.