Particle A of mass m_1 moving… - JEE Main 2020 Physics PYQ

JEE Main 2020 — Physics Mechanics

2020mcqhard

Particle $A$ of mass ${m}_{1}$ moving with velocity $(\sqrt{3}\hat{i}+\hat{j}){\mathrm{ms}}^{-1}$ collides with another particle $B$ of mass ${m}_{2}$ which is at rest initially. Let ${\vec{v}}_{1}$ and ${\vec{v}}_{2}$ be the velocities of particles $A$ and $B$ after collision respectively. If ${m}_{1}=2{m}_{2}$ and after collision ${\vec{v}}_{1}-(\hat{i}+\sqrt{3}\hat{j}){\mathrm{ms}}^{-1}$ , the angle between ${\vec{v}}_{1}$ and ${\vec{v}}_{2}$ is :

Official previous-year question

Held on 6 Sept 2020 · Verified 6 Jul 2026.

Options

A
${15}^{^{\circ}}$
B
${60}^{^{\circ}}$
C
$-{45}^{^{\circ}}$
D
${105}^{^{\circ}}$

Did you get this right?

Solution

${m}_{1}{\vec{u}}_{1}+{m}_{2}{\vec{u}}_{2}={m}_{1}{\vec{v}}_{1}+{m}_{2}{\vec{v}}_{2}$

$2{m}_{2}(\sqrt{3}\hat{i}+\hat{j})+{m}_{2}\times 0=2{m}_{2}(\hat{i}+\sqrt{3}\hat{j})+{m}_{2}\times {\vec{v}}_{2}$

$2\sqrt{3}\hat{i}+2\hat{j}=2\hat{i}+2\sqrt{3}\hat{j}+{\vec{v}}_{2}$

${\vec{v}}_{2}=(\sqrt{3}-1)\hat{i}-(\sqrt{3}-1)\hat{j}$

${\vec{v}}_{1}=\hat{i}+\sqrt{3}\hat{j}$

Angle between ${\vec{v}}_{1}$ and ${\vec{v}}_{2}$ is ${105}^{^{\circ}}$

JEE Main 2020 Physics, Center of Mass Momentum and Collision — solution figure

Your note

JEE Main Mechanics in other years

Mechanics 2026 Mechanics 2025 Mechanics 2024 Mechanics 2023 Mechanics 2022 Mechanics 2021 Mechanics 2019 Mechanics 2018 Mechanics 2017 Mechanics 2016 Mechanics 2015 Mechanics 2014

Keep practicing Mechanics

Work through every JEE Main Mechanics PYQ, year by year.

Browse all Physics topics

Solution

${m}_{1}{\vec{u}}_{1}+{m}_{2}{\vec{u}}_{2}={m}_{1}{\vec{v}}_{1}+{m}_{2}{\vec{v}}_{2}$

$2{m}_{2}(\sqrt{3}\hat{i}+\hat{j})+{m}_{2}\times 0=2{m}_{2}(\hat{i}+\sqrt{3}\hat{j})+{m}_{2}\times {\vec{v}}_{2}$

$2\sqrt{3}\hat{i}+2\hat{j}=2\hat{i}+2\sqrt{3}\hat{j}+{\vec{v}}_{2}$

${\vec{v}}_{2}=(\sqrt{3}-1)\hat{i}-(\sqrt{3}-1)\hat{j}$

${\vec{v}}_{1}=\hat{i}+\sqrt{3}\hat{j}$

Angle between ${\vec{v}}_{1}$ and ${\vec{v}}_{2}$ is ${105}^{^{\circ}}$

JEE Main 2020 Physics, Center of Mass Momentum and Collision — solution figure

Options

Did you get this right?

Solution

Your note

JEE Main Mechanics in other years

More JEE Main Mechanics questions

Other Physics topics for JEE Main

Electromagnetism

Modern Physics

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Mechanics

Options

Did you get this right?

Solution

Your note

JEE Main Mechanics in other years

More JEE Main Mechanics questions

Other Physics topics for JEE Main

Electromagnetism

Modern Physics

Optics

Thermodynamics

Waves & Oscillations

Keep practicing Mechanics