JEE Main 2023PhysicsCenter of Mass Momentum and CollisionEasyNumerical

JEE Main 2023 — Center of Mass Momentum and Collision Question with Solution

JEE Main 2023 (25 Jan Shift 2)

Question

A body of mass 1 kg collides head on elastically with a stationary body of mass 3 kg. After collision, the smaller body reverses its direction of motion and moves with a speed of 2 m s-1. The initial speed of the smaller body before collision is ______ m s-1.

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Show full solutionCorrect answer: 4
Correct answer
4

Step-by-step explanation

Let u1 be the initial speed of the smaller body before collision. 

Let v be the final speed of the bigger body after collision.

Applying conservation of linear momentum,

1×u1+0=-2+3v⇒u1=-2+3v    ...1 

We know, coefficient of restitution for elastic perfectly collision is 1.

 ⇒1=v+2u1⇒v+2=u1    ...2 

Equating 1 and 2, we have

u1=4 m s-1.

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About this question

This is a previous-year question from JEE Main 2023, 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.