# Momentum - Safety Science

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• Momentum - Safety Science
• 5) What equation is used to calculate the effect of force on momentum over a short period of time? Which two equations are put together to make it?
• F=ma, a=v-u/t. F=m*(v-u/t), F=mv-mu/t, F*t=mv-mu
• 6) For a large momentum change what must the force on an object be? If the time is decreased, what must happen to this force?
• The force must be large, the force will increase as the shorter the time for the force to act, the larger the impact force will be.
• 7) How do safety features such as air bags alter the force that a passenger has on them, as oppose to the passenger hitting the dashboard? (Talk about how time affects force to equal the change in momentum)
• The softer an object, e.g. airbag compared to dashboard, the more time you are in contact with it. The larger the time taken for the momentum change, the smaller the impact force, decreasing the chance of injury.
• 8) How do other car safety features work in a similar way to air bags? What is the sentence you have to memorize?
• Crumple zones and seat belts have a similar effect to airbags, as the increase the time for a fixed change in momentum to take place, thus decreasing the impact force.
• "These features all work by increasing the impact time to reduce the size of the impact force for a given momentum change."