Question
A bullet hits a block kept at rest on a smooth horizontal surface and gets embedded into it. Which of the following does not change?
  1. Linear momentum of the block.
  2. Kinetic energy of the block.
  3. Gravitational potential energy of the block.
  4. Temperature of the block.

Answer

  1. Gravitational potential energy of the block.

Explanation:

When the block kept at rest is hit by a bullet, the block acquires certain velocity by the conservation of linear momentum.

Therefore, the linear momentum and the kinetic energy of the block change.

As some of the kinetic energy carried by the bullet transforms into heat energy, its temperature also changes.

However, the gravitational potential energy of the block does not change, as the height of the block does not change in this process.

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