Force is the rate of change of momentum: F = Δp/Δt. For the same momentum change, a longer stopping time reduces the average force. Airbags, crumple zones and landing mats increase stopping time; use vector signs to distinguish force direction from magnitude. Example: Explain why a crumple zone reduces average force for the same initial and final momentum. It lengthens the time over which the same momentum change occurs; F = Δp/Δt therefore decreases. Use clear labels. Identify cause and effect.