Forces and Motion

Question 1

Explain how a seatbelt / crumple zone / air bag can reduce injuries? (4 marks)

Answer 1

• Force = Change in momentum / Time Taken
• Therefore, if you can increase the time taken for the momentum change the force is reduced
• An air bag / seatbelt / crumple zone increases the time taken for the momentum change
• This results in a lower force experienced
• Reduced injuries / damage

Question 2

Explain why a cannon moves in the opposite direction to the cannon ball when fired (4 marks)

Answer 2

• Momentum = Mass x Velocity
• Momentum before firing is zero
• Momentum is conserved
• After firing the cannon must have an equal and opposite momentum to the cannonball