How airbag works

28.03.2019
How airbag works

What is airbag in cars? ➤ What is the role of momentum in car crushes? ➤ How does the airbag help? ✅ Is a car airbag effective? ☝

When we hear about explosions, it creeps us out because we only think of something bad. This is true, more so in places where a lot of wars happen. But it does not always have to be a bad thing. Sometimes explosions save people’s lives too.

If for instance you are unlucky to get involved in a car accident, a good explosion may fire the airbag from the dashboard. This is why you need your airbag working the entire time cushion you from such impact. Such impacts can be fatal if you are not cushioned well. Many of the injuries resulting from accidents, and unfortunate deaths happen when someone hits on other things in car. For this reason, a safety belt ad an airbag are two things you don’t want to miss in your car.

You may not be able to avoid an accident, but you can surely do something about the level of injuries that come with it. Air backs are very simple but amazingly clever inventions. They can open at over 300km/hour faster than the car crush.

It is important to understand how an airbag works in your car. Many people only know they have these components in their vehicles, but they don’t really understand what happens with them upon an impact. Everyone one who is concerned about their safety will want to know how air bag works. And that is what we are going to discuss in this blog.

What is airbag in cars?

For years, the only thing that has been insisted upon as a car safety measure has been safety belts. Many people are not concerned about the presences of airbags until they face an accident. This is when they realize how important they are.

An airbag is an inflation system in the steering wheel or dashboard of your car. It quickly reacts and inflates at the slightest sense of a huge impact. It helps reduce risks of serious injuries that may lead to death.

What is the role of momentum in car crushes?

Momentum is the way things gain speed. And like everything else in the world, it is controlled by the law of physics. And to narrow it down, it works based on the laws of motion.

Anything that has mass (simply how much stuff in that object) has velocity (speed in a particular direction). And where speed and velocity are involved, kinetic energy is there with them. And because the car has mass and velocity, it produces the energy. The amount of kinetic energy is determined by how heavy or fast your car is. In other words, the heavier/ faster the car is, the higher the kinetic energy produced. The energy reduces when you want to stop of hit into something. At this point, the kinetic energy has to be transferred somewhere. It cannot just varnish into thin air.

Cars are designed to crumple and absorb energy. But that does not do much about the kinetic energy. It remains a huge threat to the car and the people inside.  As you increase speed, it becomes even harder to stop. It is like the car gets excited to just continue on the same path faster. This is because motion energy increases with every square of your speed.

The amount of effort you will require to stop is determined by how much kinetic energy you have built up. The more energy you have, the more you will need to lose before you can finally come to a complete halt. In case of a collision, the more kinetic energy involved, the more serious the collision. This means there are greater chances of you getting hurt or even lose your life in such a situation.

Your body is force to stop at the same speed as the abrupt stop. But then, the airbag pops out just in time to help your body stop much slower.

However, there is still a problem. The inside of a moving vehicle have mass and velocity as well. They will continue moving when the car stops abruptly. This is a brilliant law of physics discovered by Sir Isaac Newton. It states that things in motion tend to keep moving until some other forces stops them.

Cars have seatbelts to help with these issues, but they may not do the best job where a huge amount of kinetic energy is involved. The problem is, they will only restrain your body. The same force will keep going and smash into the dashboard and the windshield. This causes the airbag to come out.  Not because you have hit the area, but because the kinetic energy continues on the same path you have left. Sometimes the energy is strong it can pull out the car seat if they are not well fastened.  

How does the airbag help?

In other terms, the air bag system is referred to as a supplementary restraint system (SRS), or the supplementary inflatable system (SIR). The word supplementary is used because the airbag ‘supplements’ other safety measure. It is designed to help seat belts in protecting your life upon impact rather than replace them.

Airbag is simply an air bag. The basic airbag working principle is that it inflates as soon as the car starts to slow down due to an accident. It will do so at a much faster speed than the impact of the collision. As mentioned above, these components are quite clever. Once it has inflated, it will not remain hard. It starts to deflate as soon as your head comes in contact. The harder your head hit it, the slower it deflates to cushion you from abrupt stopping. That is very important because your head would bounce back in case the airbag fails to deflate. Relying on it alone without fastening your seat belt may not be of so much help.  

How airbag works

We have already seen the role of the airbags. It helps slow down the passenger’s forward movement as fast as possible. The air bag in cars has three important components to help it achieve this task.

  • It has the bag which is made of a thin, nylon fabric and folded in the steering wheel. There is also one in the dashboard next to the passenger. In the recent times, it is placed in the seat or door.
  • The sensor. The crash sensor in the car signals the airbag to inflate once a slight impact is felt. Inflation will happen with any force equal to running into a brick wall at a speed of about 16 to 24 km/hr (10 to 15 mph. It is connected to mechanical switch which flips when there is a shift in mass. It closes the electrical contact, sending a message to the sensor about a crash. The sensor containing an accelerometer built into a microchip, which sends the information.
  • The inflations system. This is the part of the airbag acts on the impact. It contains sodium azide (NaN3) and Potassium Nitrate (KNO3), which reacts to produce nitrogen gas. It is the hot blast of the nitrogen gas that inflates the airbag.

During the early days, the use of airbags was faced with a lot of challenges. There were prohibitive prices and technical hurdles to the systems about storage and release of this compressed gas. This made researchers scratch their heads:

  • Whether there was enough space in the car for a gas canister
  • If the gas would remain in the same state for the life of the car.
  • How to quickly and effectively expand the gas safely.

There was need to device a mechanism that set off a reaction on the chemicals to produce N3. The first development of a small solid-propellant came up in the ‘70s.

One may wonder how they work. The airbag system works by igniting a solid propellant which burns very rapidly to produce gas which fills the bag. This bag burst because it has been compressed for a long time, faster than a blink of an eye. The gas again dissipates holes on the bag which cause a quick deflation.

The whole process happens so first, is about one-twenty-fifth of a second. But any additional time is more than enough to reduce fatalities. You may also wonder what the powdery substance released from the airbag is. It is only cornstarch or talcum powder. It keeps the airbags lubricated during storage, and to help quick release.

Is a car airbag effective?

Looking at how useful they seem to be, one can assume that automobile airbags must be a good idea. However, scientists want evidence they reduce fatalities. In 1995, Adrian Lund and Susan Ferguson published a major study of road accidents. In the report, from an eight year (1985-1993) observation indicated that airbags reduced fatalities up to 23-24% for head-on collision.

This is a good observation. It is important to note however that the airbags come with violent explosions. It is just like the impact of blowing up a balloon. Though is seems easy, it can cause damage. And airbags are huge risk especially to children.  Adults may also be affected in the eyes, with possible hearing loss.

Through studies, airbags have been improved greatly, making them as safe as they are effective. Contemporary airbags for instance fire with less force but provide the same service as any other. This is why it is important to ensure you have a working airbag system in your car all the time.

Even though there are issues with the airbags, they cannot compare to how useful the systems are, and that is all that matters. Used with safety belts, these components can go a long way in ensuring you at least come out from an accident with your life.