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JEE Advanced2008PhysicsCenter of Mass, Momentum and CollisionActual

Paragraph: A small block of mass M moves on a frictionless surface of an inclined plane, as shown in figure. The angle of the incline suddenly changes from 60^ to 30^ at point B . The block is initially at rest at A . Assume that collisions between the block and the incline are totally inelastic (g=10 ~m / s ^2 ) Question: If collision between the block and the incline is completely elastic, then the vertical (upward

Options

  1. A30 ~m / s
  2. B15 ~m / s
  3. Czero
  4. D- 15 ~m / s

Correct answer

C. zero

Step-by-step solution

In elastic collision, component of v₁ parallel to B C will remain unchanged, while component perpendicular to B C will remain unchanged in magnitude but its direction will be reversed. aligned & v_ | =v₁ 30^ =( 60 ) ( 3 2 )= 45 ~ms ⁻¹ & v_ =v₁ 30^ =( 60 ) ( 1 2 )= 15 ~ms ⁻¹ aligned Now vertical component of velocity of block : aligned v & =v_ 30^ -v_ | 60^ & =( 15 ) ( 3 2 )-( 45 ) ( 1 2 )=0 aligned correct option is (c).

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