# Physics P2 3.7 Car safety.

What do seat belts and air bags do?
They spread the force across the chest and they also increase the impact time. If a driver's head hits an airbag it changes momentum slowly, so the force on the head is less than it would be if it changed momentum quickly by hitting a steering wheel.
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What do side impact bars and crumple zones do?
They 'give way' or 'fold up' in an impact so increasing the impact time and reduce the forces acting.
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How can we find out the speed of a car before an impact?
We can use the conservation of momentum. After a car crash the police use measurements from the scene and the conservation of momentum to calculate the speed of the vehicles before the collision.
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What do modern cars contain?
A number of safety features designed to reduce the forces on the occupants of the car in a collision.
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How does a seat belt work?
It stops the wearer being flung forward if the car stops suddenly. The seatbelt stretches slightly increasing the impact time and reducing the force.
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What happens to a passenger in a head-on collision if they are not wearing a seat belt?
The continue to move forwards when the car stops and will hit the windscreen.
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What happens to a passenger in a head-on collision if they were wearing a very narrow seat belt?
The narrow seat belt would not spread the force across the passenger's body and might cut them.
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**MAKE SURE THAT YOU CAN EXPLAIN HOW DIFFERENT VEHICLE SAFETY FEATURES WORK IN TERMS OF SPREADING OUT AND REDUCING THE FORCES ON THE OCCUPANTS OF THE VEHICLE**
**LOOK UP AN AIRBAG IN ACTION AND DIAGRAM OF CAR SAFETY FEATURES**
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## Other cards in this set

### Card 2

#### Front

What do side impact bars and crumple zones do?

#### Back

They 'give way' or 'fold up' in an impact so increasing the impact time and reduce the forces acting.

### Card 3

#### Front

How can we find out the speed of a car before an impact?

### Card 4

#### Front

What do modern cars contain?

### Card 5

#### Front

How does a seat belt work?