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JEE Main20202 Sep 2020Morning ShiftPhysicsCenter of Mass, Momentum and CollisionActual

A particle of mass m with an initial velocity u i ^ collides perfectly elastically with a mass 3 m at rest. It moves with a velocity v j ^ after collision, then, v is given by

Options

  1. Av = 2 3 u
  2. Bv = u 3
  3. Cv = u 2
  4. Dv = 1 6 u

Correct answer

C. v = u 2

Step-by-step solution

From momentum conservation mu i ^ + 0 = mv j ^ + 3 m v → ' v → ' = u 3 i ^ - v 3 j ^ From kinetic energy conservation 1 2 m u 2 = 1 2 m v 2 + 1 2 ( 3 m ) u 3 2 + v 3 2 solving v = u 2

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