momentum

• What is a key fact about moving objects and momentum?

  All moving objects have momentum
• What is the momentum of an object that is not moving?

  Zero
• What does the conservation of momentum state about a closed system?

  Total momentum before equals total momentum after
• In the van and car collision, how does the velocity change after the collision?

  The combined velocity is lower
• Why does the stationary car have no momentum before the collision?

  Because it is not moving
• What happens to the cannon when the cannonball is fired?

  It recoils backwards
• In a closed system, what is the relationship between the total momentum before and after an event?


  They are equal
• What is always conserved in a closed system?

  Momentum
• Why can rapid changes in momentum be dangerous?

  They can exert huge forces
• What do car manufacturers use to design safety features?

  Crash tests
• During a car crash, what happens to the momentum of the passengers?

  It falls from a large amount to zero
• In a car crash, how long does it typically take for a passenger's momentum to fall to zero?

  Less than a second
• What can be lethal during a car crash due to momentum changes?

  Huge forces
• How can the danger from rapid changes in momentum be reduced?

  Make the change happen over a longer time
• What are five safety devices that slow down momentum change?

  • Airbags in a car
  • Seatbelts in a car
  • Crash mat in athletics
  • Bike helmet
  • Cushioned surface in a playground
• What effect do safety devices have on the forces acting and the risk of injury?

  They reduce both the forces and the risk