JEE Main 2021 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 25 July 2021, Shift 2, Physics Q8

Question 8 of 90 in this shift, Physics question 8 of 30, Section A.

Two spherical soap bubbles of radii

r_1

and

r_2

in vacuum combine under isothermal conditions. The resulting bubble has a radius equal to :

(1) $\frac{r_1 + r_2}{2}$
(2) $\frac{r_1\ r_2}{r_1 + r_2}$
(3) $\sqrt{r_1\ r_2}$
(4) $\sqrt{r_1^2 + r_2^2}$ Official answer

Official answer

Option 4

NTA final key.

Chapter: Mechanical Properties of Fluids
Topic: Surface Tension
Idea tested: Isothermal Coalescence of Bubbles

Same topic in other shifts

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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.