Lesson 20.2

• Law of Conservation of Momentum


  When two objects in an isolated system collide, the total momentum of the objects before the collision is equal to the total momentum of the objects after the collision
• Momentum lost by object 1

  Equal to the momentum gained by object 2
• Newton's Third Law of Motion


  • Applied in momentum conservation
  • In billiards, the amount of force exerted by the cue ball causes the target ball to move with the same amount of force but in opposite direction
• Collision of billiard balls model the law of momentum conservation
• When the cue ball hits the target ball, momentum is transferred
• The momentum gained by the target ball is just equal to the momentum lost by the cue ball during collision
• No momentum is gained or lost in the system
• In all forms of collisions, momentum is conserved
• Whether the collision is elastic or inelastic, momentum does not change before and after collision
• Law of Conservation of Momentum (Mathematically)

  1. pbefore = pafter

  2. p1i + p2i = p1f + p2f
• pbefore


  Momentum before collision
• pafter


  Momentum after collision
• i and f


  Initial and final momentum of the objects
• Law of Conservation of Momentum (Expanded)

  m1v1i + m2v2i = m1v1f + m2v2f
• m1

  Mass of the first object
• m2

  Mass of the second object
• v1i

  Velocity of the first object before collision
• v2i

  Velocity of the second object before collision
• v1f

  Velocity of the first object after collision
• v2f

  Velocity of the second object after collision