JEE Main 2020 · PhysicsMultiple choiceSingle correctMediumMulti-step

JEE Main 2 September 2020, Shift 1, Physics Q3

Question 3 of 75 in this shift, Physics question 3 of 25.

A particle of mass

m

with an initial velocity

u\hat{i}

collides perfectly elastically with a mass

3m

at rest. It moves with a velocity

v\hat{j}

after collision, then,

v

is given by :

(1) $v=\frac{u}{\sqrt{3}}$
(2) $v=\sqrt{\frac{2}{3}}\,u$
(3) $v=\frac{u}{\sqrt{2}}$ Official answer
(4) $v=\frac{1}{\sqrt{6}}\,u$

Official answer

Option 3

NTA final key (Sep 2020).

Chapter: Work, Energy and Power
Topic: Collisions
Idea tested: Oblique Collisions

Same idea in other shifts

Asked 3× in all

8 Jan 2020, Shift 1 · Q22A body A, of mass m = 0.1 kg has an initial velocity of $3\hat{i}$ ms $^{-1}$ . It collides elastically with another body, B of the same…MediumNumerical value
6 Sep 2020, Shift 2 · Q4Particle A of mass $m_1$ moving with velocity $\left(\sqrt{3}\hat{i}+\hat{j}\right)\,\mathrm{ms^{-1}}$ collides with another particle B of…MediumSingle correct

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 42 of the 174 JEE Main shifts held from 2017 to 2026.