Momentum

• Units for momentum


  kg m/s
• Conservation of momentum principle

  Total momentum before collision = total momentum after collision
• Why do people get injured in car crashes?

  When there is a car crash the passengers decelerate rapidly

  They experience large forces because of very fast change in moment

  These large forces cause injuries
• 3 safety features that reduce risk of harm in cars

  Seat belts

  Air bags

  Crumple zones
• How do seatbelts work?

  By stretching a little bit they increase time taken for body’s momentum to reach zero, and so reduce the forces on acting on the body
• How do airbags work?

  By being flexible they increase the time taken for the bodies momentum to reach zero, and so reduce the forces acting on the body
• How do crumple zones work

  By crumpling over time they increase time taken for passengers momentum to reach zero, and so reduce forces acting on the bodies