In an isolated system, the total linear momentum

  • A. always increases
  • B. is conserved, whatever type of collision occurs
  • C. is conserved only in elastic collisions
  • D. is zero

Explanation

Momentum conservation follows from Newton's third law and holds in every collision and explosion provided no external force acts, whether the collision is elastic or not. Kinetic energy, by contrast, is conserved only in a perfectly elastic collision. This distinction is what most collision questions are really testing.

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