311 Collisions

  • All collisions are momentum conserving. But some collisions retain more KE than others.
  • A (perfectly) elastic collision is one that retains 100% of its initial total KE.
  • A perfectly inelastic collision is one that retains the minimum amount of KE.

collisionsAfast

  • Depicted above are just 5 possible outcomes of head-on collisions of two equal masses m with equal initial speed u.
  • Notice that the total momentum (of zero) is conserved for all collisions.
  • At the top is the (perfectly) elastic collision.
  • At the bottom is the perfectly inelastic collision.

collisionsBfast

  • Depicted above are just 5 possible outcomes of head-on collisions of two equal masses m, one of them with initial speed of u, and the other initially at rest.
  • Notice that the total momentum (of mu rightward) is conserved for all collisions.
  • At the top is the (perfectly) elastic collision.
  • At the bottom is the perfectly inelastic collision. (Losing all its initial KE is impossible because of momentum conservation)

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