What Is The Physics Behind The Accident
During the accident, the seatbelt exerts a huge force on the chest area and causes internal organ injury. To avoid this huge force on the chest, modern seat belts slightly release the seatbelt with the help of a torsion bar . Because of this the upper body slightly moves forward. But once the torsion bar is done with the belt release the upper bodys movement is arrested here. But the neck and head are not arrested so you can easily guess here, now what will happen? The head goes in a perfect pendulum movement in a high-speed accident. The devastation can be horrific even with the seatbelt .
This is why engineers came up with the idea of airbags. Airbags have a cushioning effect, and at the same time, prevent you from hitting the dashboard. Now I am going to explain to you about the first design of the airbag.
What Are Airbags And Why Are They Important
Airbags are inflated bags that serve as a cushion for any part of your body. They are usually found in cars and are attached in a place in front so that they can spring out of their place and cushion you from hard surfaces. They are essential for every vehicle because they play a huge role in protecting you from accidents.
While seatbelts promptly keep you strapped in your place, there is no saying how far your upper body can be injured in the face of an accident. Thus, airbag chemistry proved to be very effective, working alongside seatbelts in the function of protecting the people that travel in vehicles.
The Physics Of Airbags
Everything that happen in the world is due to physics. Car collisions are due to the laws of motion. Generally, everyone knows that the more speed you have, the more kinetic energy you are going to have . So, if you are 10 pounds and moving and 20mph, and someone weighing 20 pounds but moving at 10mph will even out. If the 10-pound person were to be moving just 1mph more, then they will make the other object move with . Now lets do this with cars. With a head- to-head collision, the kinetic energy from both cars are added up, thus making the impact worse. However, the reason an airbag is triggered is not because of the force of impact, rather, it triggers because of the drastic change of momentum. There is a chip in a car that detects changes in speed, and if you are going really fast and hit someone, you are going to slow down real fast. Once that happens, your airbags come out because you slowed down way too fast . To test this, buckle up and leave a plastic bottle on the passenger seat that isnt buckled up or restrained, drive on an open road and hit the brakes abruptly. The seatbelt should reduce your speed gradually but the water bottle should fling into the dashboard at that same speed that you were at before you hit the brakes. The only reason you can survive a high impact collision is because the seatbelt and airbags displace the full impact over time. The more time in between an impact, the less damage you will take.
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Video: How Airbags Work
Normally, something blowing up in your face is bad. But in the event of a vehicle accident, and in conjunction with a seatbelt, one particular explosion could very well save your life. It’s the chemical reaction that inflates your airbags.
In this episode of Reactions, learn about the past and present of vehicle airbags and the lifesaving chemistry and physics that make them work:
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Trucks: More Likely To ‘win’ In Car Crash
Phil Frame, a spokesman for the National Transportation Safety Board, said that while large trucks are not part of most deadly wrecks, “they are overrepresented in the number of fatal accidents they are involved in.”
In 1997, they accounted for 9 percent nationally of all vehicles in fatal wrecks, but accounted for only 3 percent of all registered vehicles and 7 percent of total vehicle miles traveled, the national transportation statistics show.
“The greater mass vehicle almost always wins in a vehicle crash”, Frame said.
78 percent of the people who died after collisions with big trucks were occupants of the other vehicle, and 75 percent of the people who were injured were in the other vehicle.”
Excerpts from “Facts counter fear about big rigs”, by Jennifer Brett, Atlanta Journal.
Spokesmen for the trucking industry are quick to point out that truck drivers are better trained, and safer drivers than the general public – and that is believable. But just the physics of collisions dictates that the occupant of the less massive vehicle is more at risk when a collision does occur.
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How Are They Activated In Cars
Since NaN3 reacts at high temperatures, there are collision sensors attached in front of a car which takes advantage of this property. As soon as a collision is sensed, an igniter compound is produced, which is responsible for raising the temperature causing the compound of NaN to break and produce the N2, which inflates the airbag in about 30 seconds.
Padding As Protection During Sports
The same principle explains why wicket keepers in cricket use padded gloves or why there are padded mats in gymnastics. In cricket, when the wicket keeper catches the ball, the padding is slightly compressible, thus reducing the effect of the force on the wicket keepers hands. Similarly, if a gymnast falls, the padding compresses and reduces the effect of the force on the gymnast’s body.
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How Effective Are Airbags
Airbags sound like they must be a good idea, but scientists like hard evidence: isthere any proof that they reduce fatalities?In 1995, Adrian Lund and Susan Ferguson published a major study of road traffic accidents over eight years from 1985 to 1993. They found that airbags reduced fatalities by 2324 percent in head-on crashes and by 16 percent in crashes of all kinds, compared to cars fitted only with manual safety belts.
That’s obviously a huge improvement, but it’s important to note that airbags are violently explosive things that present dangers of their own. The biggest risk is to young children, though adults also face a small risk ofeye injury and hearing loss.If an airbag saves your life, you probably consider a slight risk of injury a price well worth paying. Even so, it’s clearly important to study the potential dangers of airbags so we can make them as safe and effective as possible.Modern airbags fire with less force than older designs,and there’s compelling evidence that this has reduced accidental deaths, especially among children, without compromising passenger safety.
Dual Stages Of Deployment
Recently, a new design has created an innovative class of smart airbags. These airbags are designed to deploy at two different speeds and may not deploy at all depending on the information that the computer receives. Information from sensors beneath the seats and the seat belts let the airbags know the severity of the accident. In minor crashes, the airbags deploy at 70 percent of their full force. With more severe crashes, dual deployment occurs and the airbags operate at full force. Sensors within the seats operate to weigh the passengers, so the airbags only deploy if the passenger weighs a certain amount. This helps to prevent injuries from occurring among lighter adults and children.
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Put Your Seat Belts On
To avoid such a situation:
An airbag, quite appropriately is also known as a supplementary inflatable restraint . The prefix supplementary means that airbags are meant to supplement seat belts when it comes to protecting the vehicle occupants. On the other hand, disregarding seat belts and relying entirely on the airbag could be a very risky undertaking. In fact, in some cars, an airbag wont even be fully functional if some energy of the forward-thrown occupant is not absorbed by the seatbelt.
Remember, an airbag only supplements the effectiveness of your seat belt to put it plainly, its really a good idea to wear your seat belt at all times!
How Does An Airbag Work Chemistry
The answer would be found in a fascinating chemical called sodium azide, NaN3. When this substance is ignited by a spark it releases nitrogen gas which can instantly inflate an airbag. … An airbag is designed to release some of the gas just after it deploys to help cushion the impact against the body.
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Physics In Action: Impulse
A very important application of impulse is improving safety and reducing injuries. In many cases, an object needs to be brought to rest from a certain initial velocity. This means there is a certain specified change in momentum. If the time during which the momentum changes can be increased then the force that must be applied will be less and so it will cause less damage. This is the principle behind arrestor beds for trucks, airbags, and bending your knees when you jump off a chair and land on the ground.
Do Airbags Really Save Lives
According to NHTSA data: In frontal crashes, frontal air bags reduce driver fatalities by 29 percent and fatalities of front-seat passengers age 13 and older by 32 percent. NHTSA estimates that the combination of an air bag plus a seat belt reduces the risk of death in frontal crashes by 61 percent.
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How Do Airbags Work In A Car
In a collision, airbags are intended to lessen head injuries. They achieve this by providing head and neck protection during the forward momentum brought on by the abrupt stop, also known as a crash.
What causes this to occur?
A moving object, like your car, has mass, as we all hopefully learned in our high school physics classes. Your car has a velocity because it is moving, and velocity is an objects speed in a particular direction. An object has kinetic energy when those two conditions are met. The kinetic energy increases with increasing mass and velocity.
Manufacturers have implemented seatbelts to address that issue. They existed long before airbags. But seatbelts cant shield someones head or neck from harm.
Ironically, the seatbelts force will cause the top of your body, namely your head and neck, to suddenly move forward. That could seriously harm your neck muscles, and of course, theres a good chance that youll hit your head on the steering wheel or dash. As a result, the main purpose of an airbag is to protect your neck and head.
Here are also some types of airbags. There are different types of airbags, as weve previously stated, and these are mounted in significant areas of a vehicle:
Why Car Crashes Do Damage
Like everything else in the world,car crashes are controlled by the laws of physicsand, more specifically, the laws of motion.
Anything that moves has mass and velocity. Anything that has mass and velocity haskinetic energy, and the heavier your car andthe faster you’re going, the more kinetic energy it has. That’s fine until you suddenly wantto stopor until you crash into something. Then all the energy hasto go somewhere. Even though cars are designed to crumple up andabsorb impacts, their energy still poses a major risk to thedriver and passengers.
Chart: The faster you go, the harder it is to stop. That’s because your kinetic energy increaseswith the square of your speed . The more kinetic energy you have, the more you needto lose before you come to a stop. If a collision brings your car to a halt in a certain time, the more energy you have, the moreviolent the collision, and the greater the chance you’ll be injured or killed. Airbags help your body stop more slowly,reducing the risk of injury and death.
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How Is Chemistry Applied In The Manufacturing Of Airbags
Airbags contain a compound known as sodium azide, which is quite stable at normal temperature, and no changes occur in the airbag. But, at a higher temperature, this compound breaks down into its subsequent products of sodium and nitrogen. Thus, airbags do not contain air as the name implies but are filled with nitrogen.
What Is Airbag System
An airbag is a vehicle occupant-restraint system using a bag designed to inflate extremely quickly, then quickly deflate during a collision. … During a crash, the vehicle’s crash sensors provide crucial information to the airbag electronic controller unit , including collision type, angle, and severity of impact.
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Airbag: The First Practical Design
The Great founder of Joyson safety systems, Mr. Allen K. Breed, came up with some groundbreaking inventions to solve the above issues.
1)First, he improved the accuracy of the sensor using a ball-in-tube sensor. In this sensor, a steel ball is held in position with the help of a magnet as shown in Fig: 3A below.
2)And the second contribution is the use of sodium azide chemical explosives. Explosion of sodium azide generates nitrogen gas which is used to inflate the airbag. This is a quick and reliable reaction which removes the necessity of storing the compressed air onboard. The sodium azide is stored in an airtight cylinder inside the steering wheel you can see in the Fig: 3B.
Why Is Nitrogen Gas Used In Airbags
Why is nitrogen gas used in airbags? Sensors in the front of a vehicle detect a collision sending an electrical signal to a canister that contains sodium azide detonating a small amount of an igniter compound. The heat from the ignition causes nitrogen gas to generate, fully inflating the airbag in .
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The Deflation On Impact
After the bag has done its job and saved you from flyingforwards, it also has to make sure it doesnt knock you back with even moreforce than there was before. A reaction that fast could push you even harderthan you already could be after all. To do that, the bag has to minimise theblow as soon as you collide with it.
To do that, the bag actually deflates almost as fast as itinflates. As soon as you impact with the bag, the gasses are pushed out ofholes all around the bag to make it deflate. That prevents a bouncing effect ofthe bag and means your neck doesnt slam you back into the seat. Its really anextremely intelligent invention.
Deployment Of An Airbag
The moment a vehicle crashes into something, it slows down rapidly, or in technical terms, begins to decelerate at a high rate. Just think of how abruptly a car stops after crashing that means that the deceleration would be quick and highly dangerous.
Upon impact, an electronic chip, known as an accelerometer, instantly detects the sudden change in the speed of the vehicle. If this change is greater than the deployment threshold, the airbag circuit is triggered.
Current is passed through a heating element, which in turn ignites an explosive . A large amount of harmless gas instantly fills the nylon bag installed behind the steering wheel as the explosive burns. At that point, the plastic cover is torn off the steering wheel and the bag inflates , and lo and behold A protective pillow for your face!
The airbag is deployed!
As the driver pushes against the inflated airbag, it begins to deflate as the gas escapes through small holes around the edges of the bag. The airbag should already be deflated completely once the car becomes absolutely stationary.
A deflated airbag
So, thats how an airbag works!
However, after seeing that so many things have to occur before the actual deployment of the airbag occurs, doesnt it seem to be a rather time-consuming process? How can this possibly protect you in time a car crash happens so fast!
On average, the entire process of deployment of an airbag completes in 0.120 seconds, depending on the vehicle and the design of the airbag.
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How Effective Are Airbags And Seatbelts
“Note also that the effectiveness of a belt-bag system is somewhat less than the sum of the effectiveness ratings of its two components. ” The study says belts are 48 percent effective in preventing fatalities, while airbags are 14 percent effective. But added together, they’re just 53.72 percent effective.
The Insane Physics Of Airbags
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I can imagine the meeting: A dozen engineers are gathered around a conference table to discuss automobile safety. How can we protect people during a car crash? We have already added seat belts and crumple zones to cars. Is there anything else we can include? One attendee reluctantly raises their hand with a suggestion: “How about we add an explosive in the steering wheel?” Brilliant. That’s exactly what we will do. We will put a bomb in the car and it will save lives.
They were right. Airbags are explosives and airbags save livesbut it’s still a crazy idea.
The original idea for the automotive airbag dates back to the early 1950s. It wasn’t exactly an explosive-powered device. It involved a compressed gas that would release to fill a type of bladder. This design didn’t work very wellit wasn’t fast enough. It turns out the only way to get an airbag to inflate fast enough to be useful is with an explosive. OK, technically it’s a chemical reaction that produces gas to fill the bagbut that’s essentially an explosion.
So, just how fast does the airbag need to inflate? Let’s do a rough estimation to get the minimum inflation time.
It’s even crazier than you think. Let’s imagine what has to happen for this collision .
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