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JEE Main 20203 SeptemberEvening Shift
Exam
JEE Main
Year
2020
Date
3 September
Shift
Evening Shift
Subject
Physics
Chapter
Center of Mass, Momentum and Collision

JEE Main 2020 · 3 September · Evening Shift · Physics · Center of Mass, Momentum and Collision

A block of mass 1 . 9kg is at rest at the edge of a table, of...

A block of mass 1.9kg1 . 9kg is at rest at the edge of a table, of height 1 m. A bullet of mass 0.1kg0 . 1kg collides with the block and sticks to it. If the velocity of the bullet is 20ms−120m{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=10ms−2g = 10m{s}^{- 2}. Assume there is no rotational motion and loss of energy after the collision is negligible.]

Options

  1. A21J21J
  2. B20J20J
  3. C19J19J
  4. D23J23J

Correct answer

A. 21J21J

Step-by-step solution

Conservation of linear momentum

0.1×20=(0.1+1.9)×v0 . 1 \times 20 = \left(0 . 1 + 1 . 9\right) \times v

v=1ms−1v = 1m{s}^{- 1}

Using work energy theorem

Wg=∆k{W}_{g} = ∆ k

2×g×1=k−12×2×122 \times g \times 1 = k - \dfrac{1}{2} \times 2 \times {1}^{2}

∴k=21J∴ k = 21J

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