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# How do seat belts work? watch

1. Can someone explain to me how they work.
2. Keep you in your seat and also give a little so that you're brought to rest over a longer period of time, meaning that your deceleration is less and there is less force on you.
3. Nah, they're just there for design...

... -.-
4. (Original post by Super199)
Can someone explain to me how they work.
When stretching seatbelts cause a smaller deceleration of the persons body this is done by increasing the time over which the force can act. since a = v-u/t increasing t decreases a,(acceleration). since F=ma, smalller a will result in a smaller F.
5. Seatbelts also prevent collisions with a windscreen, which would lead to a sudden deceleration, and as F=ma, higher a -> higher F -> more chance of injury
6. Seat belts are designed to increase the time taken for impact...this reduces the impulse you experience.
7. How do crumple zones and air bags work?
8. Like seatbelts, both length the time it takes to go from whatever the initial velocity was prior to impact to zero.

Crumple zones are areas of a vehicle which are specifically designed to deform on impact. If the front end of a vehicle was completely rigid and very strong, no deformation (compression) would occur on impact and the vehicle may come to a standstill in a very short period of time/distance, inflicting huge deceleration forces on the occupants and thereby possibly causing trauma/organ damage and all sorts of nasty injuries.

Airbags are as the name implies. They reside in steering wheels, dashboards, and now in the sides of seats, overhead in roofs, even under steering racks. When a vehicle registers a large impact, they are pressurised with compressed gas very quickly to provide a cushion, which will prevent occupants from hitting hard surfaces and registering large deceleration forces.
9. Need help with an exam question. The last question on this paper.....

http://www.ocr.org.uk/Images/79221-q...-mechanics.pdf
10. The whole of 6 (d)? Or just part of it?
11. (Original post by Super199)
Need help with an exam question. The last question on this paper.....

http://www.ocr.org.uk/Images/79221-q...-mechanics.pdf
Guy's, can you please post new questions as a new thread as others will be interested in learning from them as well. i.e. the original thread title bears no resemblance to the content of the thread at this point and will be missed by others.

Thanks.

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