Grade 12 Physics Applications: Safety Features Relating to Impulse
Seat Belts
Seat belts stop you tumbling around inside the car if there is a collision. However, they are designed to stretch a bit in a collision, because the material has some give to it. This increases the time taken for the body's momentum to reach zero, so it reduces the forces on it. (i.e. on the heart and internal organs within the body). When encountering a car collision, the driver and passenger tend to keep moving in accord with Newton's first law. Their motion carries them forward, but the nature of the seatbelt's structure is that it has give. Therefore the body continues to move forward, but at a slower speed. This increases collision time and mimimizes forces and making sure the body (and it's internal organs) do not get injured or experience trauma.
Air Bags
Air bags are used in automobiles because they are able to minimize the effect of the force on an object involved in a collision. This is because they increase the time taken for the head's momentum to reach zero, so they reduce the forces on it. When encountering a car collision, the driver and passenger tend to keep moving in accord with Newton's first law. Their motion carries them towards a windshield that results in a large force exerted over a short period of time in order to stop their momentum. If instead of hitting the windshield, the driver and passenger hit an air bag, then the time duration of the impact is increased. This is possible because the material has some give. Airbags also act as soft cushions and prevent cuts.
Padded Dash Boards
If a car does not contain airbags, or the air bags do not deploy, then both a driver and their passengers run the risk of stopping their momentum by way of collision with the windshield or dashboard. If the driver or passenger should hit the dashboard, then the force and time required to stop their momentum is exerted by the dashboard. Padded dashboards provide some give in such a collision and serve to extend the time duration of the impact, thus minimizing the effect of the force. That said, this give is considerably less compared to that of an airbag.
Crumple Zones
Crumple zones are areas of a vehicle that are designed to crush in a controlled way in a collision. They increase the time taken to change the momentum in a crash, which reduces the force involved in a way similar to seatbelts, airbags and padded dash boards (as discussed above).
What Does "Give" Mean?
The term give, as used above, refers to when an object is more elastic and soft. By this I mean an object is not so solid, and is thereby able to move with the object and reduce force by increasing collision duration. An object with give makes a collision more inelastic.
