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JEE Main20199 Apr 2019Morning ShiftPhysicsCenter of Mass, Momentum and CollisionActual

A body of mass 2 k g makes an elastic collision with a second body at rest and continues to move in the original direction but with one fourth of its original speed. What is the mass of the second body?

Options

  1. A1.8 k g
  2. B1.2 k g
  3. C1.0 k g
  4. D1.5 k g

Correct answer

B. 1.2 k g

Step-by-step solution

From conservation of linear momentum m U = m U 4 + M V . . . (i) For elastic collision: e = 1 = V - U 4 u V = 5 U 4 . . . (ii) From equation (i) & (ii), m U = m U 4 + M 5 U 4 m = m 4 + 5 4 M ⇒ M = 3 m 5 = 1.2 k g

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