Momentum & Safety Features
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Safety features in vehicles
When a car stops abruptly, its passengers keep moving — and the faster that momentum is brought to zero, the harder the hit. Every safety device in a vehicle works the same trick: stretching out the stopping time so the force shrinks. This lesson follows that idea through seat belts, airbags and crumple zones.
What you know already
You already know that every moving object carries momentum, and that a force acting over a time changes it. This lesson puts that idea to work: seat belts, airbags, crumple zones and crash mats all manipulate one quantity — the time a collision lasts — to cut the forces a body feels.
Key points of understanding
- Force equals the rate of change of momentum, so lengthening the collision time lowers the force the impact delivers.
- Contact time is how long the person stays in touch with whatever they have hit.
- Crumple zones, seat belts and airbags absorb impact energy by changing shape, stretching the duration of the force.
- A stretched seat belt gives the passenger's momentum longer to fall to zero, cutting the force felt.
- Airbags cushion passengers thrown forwards, and crumple zones crush deliberately at the front and rear to extend the stopping time.
- A heavy, fast vehicle carries huge momentum, so only an extended contact time can keep its impact force down.
The seat belt, airbag and crumple zones help reduce the risk of injury on a passenger
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1.Safety features in vehicles
When a car stops abruptly, its passengers keep moving — and the faster that momentum is brought to zero, the harder the hit. Every safety device in a vehicle works the same trick: stretching out the stopping time so the force shrinks. This lesson follows that idea through seat belts, airbags and crumple zones.
The seat belt, airbag and crumple zones help reduce the risk of injury on a passenger
Key points
- Force equals the rate of change of momentum, so lengthening the collision time lowers the force the impact delivers.
- Contact time is how long the person stays in touch with whatever they have hit.
- Crumple zones, seat belts and airbags absorb impact energy by changing shape, stretching the duration of the force.
Guided content from the SME authoring corpus — note rn_RQK2MW3zRPNNzwtc, pinned at 0cea83a78102 · promoted SyllabAI/syllabai-resources b3caaaa90c5e
