Airbags explode out to the car at over 300 km/h which is much faster than a car can crash, helping in the cushioning the impact and reduce the damage to the body. The person inside the moving car will have a mass and velocity even when the car stops, and will tend to keep on going. As mentioned in the law of physics or Newton’s first law of motion – the things that are moving tend to keep on moving until a force stops them. The seatbelt protect the body, but not the head. The head weighs 3-6 kg and even if the body is fastened tightly with the seat belt, the head will keep on going and smash into the steering wheel and windshield.
Airbag is also called Supplementary Restraint System (SRS) or Supplementary Inflatable Restraint (SIR). The airbag is made to support the seat belts protect the person instead of replacing them. Hence relying on an airbag to protect the person without fastening the seat belt is dangerous. The airbags inflates as soon as the car starts to slow down in an accident and deflates as the head presses against it. If the bag does not deflate, the head would bounce back off.
How does airbag work?
When a car hits something, it starts to lose the speed extremely fast. The accelerometer which is the electronic chip that measures the acceleration or force detects the change in speed. If the deceleration is more, the accelerometer triggers the airbag circuit. The point to be noted here is that the normal brake that we apply does not generate enough force to do this. The airbag circuit passes an electric current through a heating element which is similar to one of the wires in toaster. The heating element ignites the chemical explosive. When the explosive burns, it generates a massive amount of gas which is harmless – nitrogen or argon – which floods into the nylon bag which is packed behind the steering wheel.
When the bag expands, it blows the plastic cover off the steering wheel and inflates. The bag is coated with a chalky substance similar to talcum powder to help it unwrap smoothly. The driver falls on the airbag which makes the bag to deflate as the gas it contains escapes through the small holes around its edges. By the time the car stops, the bag will be completely deflated.
Disadvantage of airbags:
Airbags pose a greater risk to passengers who are shorter than average. Moreover, the airbag is not a replacement to the seat belts. If a person is not wearing the seat belt, there are higher chances of the person getting hurt and even killed by the deployment of airbag. It is not safe to carry the children on the lap for the same reason.
Moreover, even in a small, low impact crash of as little as 10 miles per hour the air bag may deploy. The cost of replacing the air bag and the damage to the dashboard will be high.