JEE Main 2021PhysicsCenter of Mass Momentum and CollisionHardNumerical

JEE Main 2021 — Center of Mass Momentum and Collision Question with Solution

JEE Main 2021 (25 Jul Shift 1)

Question

A body of mass 2 kg moving with a speed of 4 m s-1 makes an elastic collision with another body at rest and continues to move in the original direction but with one fourth of its initial speed. The speed of the two body centre of mass is . Find the value of x.

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Show full solutionCorrect answer: 25
Correct answer
25

Step-by-step explanation

pi=pf

2×4=2×1+m2×v2

m2v2=6 …(1)

By coefficient of restitution, 
1=v2-14⇒v2=5 m s-1

by (i)

m2×5=6

m2=1.2 kg

vcm=m1v1+m2v2 m1+m2

vcm=2×1+1.2×52+1.2=83.2=2510

x=25

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About this question

This is a previous-year question from JEE Main 2021, covering the Center of Mass Momentum and Collision chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.