5.7

• What is the equation used to calculate an object’s momentum?

  Momentum = Mass x Velocity
• What is the unit used for momentum?


  kg m/s
• What can be said about the momentum before and after a collision in a closed system?


  The total momentum before is equal to the total momentum afterwards.
• What is the equation linking change in momentum, force, and time?


  Force x Time = Change in Momentum
• What quantity is equal to the force experienced in a collision?


  The rate of change of momentum.
• If an object’s change of momentum is fixed, how can the force experienced by the object be reduced?


  By increasing the length of time over which the change of momentum occurs.
• How does a seatbelt improve a passenger’s safety during a collision?

  • Passenger decelerates from the vehicle’s velocity at impact to zero, undergoing a fixed change of momentum.
  • The force experienced is equal to the rate of change of momentum.
  • Seatbelts increase the time over which the force is applied, reducing the rate of change of momentum and therefore reducing the force experienced.