Momentum & Safety Flashcards
All 6 cards in this deck
What are the three steps in explaining how a safety feature reduces injury?
e.g. a cycle helmet in a crash
- It increases the time taken to stop (the contact time)
- So the rate of change of momentum decreases
- So the force on the person is reduced
What effect do air bags and seat belts have on the time taken for a passenger's momentum to fall to zero?
They increase it, so the rate of change of momentum, and therefore the force, is smaller.
Why are playground surfaces and gymnasium crash mats cushioned?
They increase the time taken to stop a falling person, reducing the rate of change of momentum and so the force on them.
True or false? An air bag works by reducing the passenger's change in momentum.
False. The change in momentum is the same; the air bag increases the time for that change, reducing the force.
True or false? A seat belt that stretches slightly in a crash increases the force on the wearer.
False. Stretching increases the stopping time, so the force on the wearer is reduced.
True or false? Saying a crash mat 'slows down time' is an acceptable explanation of how it reduces injury.
False. You must say it increases the time taken to stop, reducing the rate of change of momentum and so the force.