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NTA Abhyas JEE Main2020PhysicsCenter of Mass, Momentum and CollisionPractice

Two particles A and B each of mass m are attached by a light inextensible string of length 2 l . The whole system lies on a smooth horizontal table with B initially at a distance l from A . The particle at the end B is projected across the table with speed u perpendicular to A B . The velocity of the ball A just after the string is taut, is

Options

  1. Au 3 4
  2. Bu 3
  3. Cu 3 2
  4. Du 2

Correct answer

A. u 3 4

Step-by-step solution

When the string jerk tight both particles begin to move with velocity components v in the direction A B . Using conservation of momentum in the direction A B m u cos ⁡ 30 ° = m v + m v or v = u 3 4 Hence, the velocity of ball A just after the jerk is u 3 4

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