Momentum

• All moving objects have momentum but if an object is not moving then its momentum is zero
• Momentum


  Mass multiplied by velocity
• The unit of momentum is kilograms meter per second
• Calculating momentum


  • Car with mass 1,000 kg and not moving: momentum = 0
  • Car with mass 1,000 kg and moving at 20 m/s: momentum = 20,000 kg m/s
• Conservation of momentum


  In a closed system, the total momentum before an event is equal to the total momentum after an event
• Example 1: Van colliding with stationary car

  1. Van has momentum before collision

  2. Van and car move together at lower velocity after collision

  3. Total momentum before = total momentum after
• Example 2: Cannon firing cannonball

  1. Cannon and cannonball have zero momentum before firing

  2. Cannonball has forward momentum after firing

  3. Cannon has backward momentum after firing

  4. Total momentum before = total momentum after