A block of mass 1 . 9   kg is at rest at the edge of a table, of height 1 m. A bullet of mass 0 . 1…

A block of mass 1.9 kg is at rest at the edge of a table, of height 1 m. A bullet of mass 0.1 kg collides with the block and sticks to it. If the velocity of the bullet is 20 m s-1 in the horizontal direction just before the collision then the kinetic energy just before the combined system strikes the floor, is [Take g = 10 m s-2. Assume there is no rotational motion and loss of energy after the collision is negligible.]
  1. 21 J
  2. 20 J
  3. 19 J
  4. 23 J

Solution

Conservation of linear momentum

0.1×20=0.1+1.9×v

v=1 m s-1

Using work energy theorem

Wg=k

2×g×1=k-12×2×12

   k=21 J

Asked in: JEE Main 2020 (03 Sep Shift 2)

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