JEE Main 2021PhysicsCenter of Mass Momentum and CollisionMediumMCQ

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

JEE Main 2021 (27 Jul Shift 1)

Question

Three objects A, B and C are kept in a straight line on a frictionless horizontal surface. The masses of A, B and C are m, 2m and 2m respectively. A moves towards B with a speed of 9 m s-1 and makes an elastic collision with it. Thereafter B makes a completely inelastic collision with C. All motions occur along the same straight line. The final speed of C is :

Choose an option

Show full solutionCorrect option: D
Correct answer
D3 m s-1

Step-by-step explanation

Collision between A and B

m×9=mv1+2 mv2 (from momentum conservation)
e=1=v2-v19
⇒v2=6 m sec-1, v1=-3 m sec-1
Collision between B and C

2 m×6=4mv (from momentum conservation)
v=3 m s-1

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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.