Airbags |Need of airbags |Working of airbags

How we get hurt during accident?

Let us understand Need of airbags with the help of laws of motion, We all know that moving objects have momentum and according to low of motion objects under motion or under momentum will remain in motion unless any external force is applied.

In case of human sitting inside the moving car and when car achieves certain speed, both objects (Human & car) are under motion and they require external force, friction between roads and Tyre in this case and some amount of time for steady or smooth stoppage.

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But during accidents especially during head to head collisions, if speed of car is such that taking it to zero by applying external force or brake requires some amount of time, The speed instantly drops to zero. Body and parts of car are grouped or united as a single entity but human sitting inside car is like freely falling body. So car comes to zero speed instantly but human sitting inside continues to retain the momentum and thus hits the front portion of the car with the speed of car.

If car hits a body in rest, Momentum of car reduces from full speed to zero and if car hits another car coming towards it then momentum reduces from full speed to negative and then to zero.

How airbag works?

Airbag is consist of mainly three components:

1 Bag: Bag is part of the airbag which protects human to hit on dashboard and is made up of thin fabric, Generally of nylon and is assembled inside the steering wheel top cover for driver and under dashboard for person sitting on side seat. In few expensive cars they provide airbags under doors to protect from side collisions. Bags are assembled in folded condition and folding is done considering quick unfolding i.e.within fraction of seconds.

:Picture source: howstuffworks

2 Sensor: Sensor is a electronic device which tells the inflation system to inflate the bag. Air bag Sensor has one mechanical switch located at the front end of car, this sends the information to chip about the collision and further information is sent to the inflation system. According to the information received from the switch, chip decides the intensity of crash.

3. Inflation system: Inflation system is the electronic unit which gets information about the crash and triggers the chemical reactions so that bag can inflate. This system has chemical required for inflation and the igniter compound for starting the reaction. This chemical used in airbags is Sodium azide ( NaN3).

Whenever accidents takes place, first system which comes into play is the sensor, this sensor after analyzing the speed, intensity and impact of crash sends information to the inflation system.

Inflation system triggers the chemical reaction by depositing the iginter compound in the sodium azide, hereby starting the reaction:
2NaN3 ——————-> 2 Na + 3 N2 This reaction releases large amount of N2 nitrogen gas which is responsible for inflation. This reaction also produces Sodium which is harmful for human body so to minimize that, manufacturers add some more chemicals to it. This whole set of processes takes place with in fraction of seconds.

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