JEE Main 2021 · PhysicsNumerical answerNumerical valueMediumCalculation

JEE Main 26 August 2021, Shift 1, Physics Q23

Question 23 of 90 in this shift, Physics question 23 of 30, Section B.

A soap bubble of radius 3 cm is formed inside the another soap bubble of radius 6 cm. The radius of an equivalent soap bubble which has the same excess pressure as inside the smaller bubble with respect to the atmospheric pressure is __________ cm.

Official answer

NTA final key.

Chapter: Mechanical Properties of Fluids
Topic: Surface Tension
Idea tested: Pressure in Concentric Soap Bubbles

Same topic in other shifts

All Surface Tension questions

2 Apr 2026, Shift 1 · Q45A liquid drop of diameter $2$ mm breaks into $512$ droplets. The change in surface energy is $\alpha\times10^{-6}$ J. The value of…EasySingle correct
2 Apr 2026, Shift 2 · Q33The surface tension of a soap bubble is 0.03 N/m. The work done in increasing the diameter of bubble from 2 cm to 6 cm is…EasySingle correct
4 Apr 2026, Shift 1 · Q47The surface tension of a soap solution is $3.5\times10^{-2}$ N/m. The work required to increase the radius of a soap bubble from $1$ cm to…MediumNumerical value
5 Apr 2026, Shift 2 · Q33Eight mercury drops, each of radius $r$ , coalesce to form a bigger drop. The surface energy released in this process is __________. (S is…EasySingle correct
2 Apr 2025, Shift 2 · Q31Two water drops each of radius $r$ coalesce to form a bigger drop. If $T$ is the surface tension, the surface energy released in this…EasySingle correct
3 Apr 2025, Shift 2 · Q47The excess pressure inside a soap bubble A in air is half the excess pressure inside another soap bubble B in air. If the volume of the…EasyNumerical value

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.