JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumConceptual

JEE Main 17 March 2021, Shift 1, Physics Q9

Question 9 of 90 in this shift, Physics question 9 of 30, Section A.

When two soap bubbles of radii a and b (b > a) coalesce, the radius of curvature of common surface is :

(1) $\frac{ab}{b-a}$ Official answer
(2) $\frac{ab}{a+b}$
(3) $\frac{b-a}{ab}$
(4) $\frac{a+b}{ab}$

Official answer

Option 1

NTA final key.

Chapter: Mechanical Properties of Fluids
Topic: Surface Tension
Idea tested: Common Interface of Coalescing Bubbles

Same topic in other shifts

All Surface Tension questions

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Question text from the official JEE Main paper published by NTA; answer from the final answer key. Chapter, topic and idea tags, difficulty and skill are Lumi’s. Lumi analyses 108 of the 174 JEE Main shifts held from 2017 to 2026.