A bag that fills with air to protect a driver or passenger when a vehicle crashes.
Who invented airbags?
If you search around online, you'll find quite a few different people are credited with inventing airbags. Who thought of them first? It appears to have been John W. Hetrick of Newport, Pennsylvania, who came up with the idea after an accident in which he swerved his car off the road into a ditch to avoid hitting a rock, almost throwing his daughter through the windshield. Hetrick filed his patent for a Safety cushion assembly for automotive vehicles on August 5, 1952 (it was granted as US Patent #2,649,311 on August 18, 1953). Although a German inventor named Walter Linderer filed an airbag patent several months before Hetrick, it was granted after Hetrick's, and it seems likely that the two men came up with the same idea independently. Many other inventors have built on the idea since then, notably Allen K. Breed (1927–2000), who developed a variety of different ways of triggering the explosion of gas inside an airbag just before the impact of a crash. According to Breed's New York Times obituary, he made his first airbag design in 1968, and filed numerous patents for improvements, helping to turn Breed Corporation into one of the world's largest suppliers of car safety systems.
Definition of AIR BAG:
an automobile safety device consisting of a bag designed to inflate automatically especially in front of an occupant in case of collision.
Objects
in a car have mass, speed and direction. If the object, such as a
person, is not secured
in the car they will continue moving
in the same direction (forward) with the same speed (the speed the car
was going) when
the car abruptly stops until a force
acts on them.
Every object has momentum. Momentum is the product of a passenger's mass
and velocity ( speed with a
direction). In order to stop the passenger's momentum they have to be
acted on
by a force. In some situations the
passenger hits into the dashboard or windshield which acts as a force
stopping them but
injuring them at the same time.
An airbag provides a force over time. This is known as impulse. The more time the force has
to act on the passenger to slow them down, the less damage caused to the passenger
There is a restricted amount of time that the airbag has to act between when the car hits
the other object and the passenger hits the steering wheel.
- About 15 to 20 milliseconds after the collision occurs the crash sensors decide whether or not the collision is serious enough to inflate the airbag (usually 6 - 10 km/h).
- If the crash sensors decide to inflate the airbag it will be deflated at about 25 milliseconds after the crash.
- It takes about 20 milliseconds to inflate the airbag for the person to land into.
- Around 60 milliseconds the person has made contact with the airbag and the airbag now starts to deflate.
- The passenger continues to be acted on by the airbag as it is in the deflation process which takes about 35 to 40 milliseconds.
It is still necessary to wear a seat belt although all automobiles must be equipped with an airbag
because of a few reasons:
1) The crash sensors do not signal for the airbag to inflate unless the vehicle is moving at least 6 km/h. Damage can still occur to the passenger if the collision is of a slower speed. This is were the seat belt plays an important role.
2) The airbag located in the steering wheel does not help the passenger in a collision where another car hits them side on.
3) When the car the passenger is in is backing up and collides the its rear end with another object the airbag does not help.
With today's technology other airbags are being introduced in addition to the steering wheel airbag and the passenger airbag. Such airbags that are being introduced are side airbags and head airbags.
Like everything else in the world, car crashes are controlled by the laws of physics—and, more specifically, the laws of motion. Anything that moves has mass (very loosely speaking, this means how much "stuff" an object contains and it's closely related to how heavy it feels) and velocity (loosely, this is the same thing as speed, but strictly it means speed in a certain direction). Anything that has mass and velocity has kinetic energy, and the heavier your car and the faster you're going, the more kinetic energy it has. That's fine until you suddenly want to stop—or until you crash into something. Then all the energy has to go somewhere. Even though cars are designed to crumple up and absorb impacts, their energy still poses a major risk to the driver and passengers.
The trouble is, people inside a moving car have mass and velocity too and, even if the car stops, they'll tend to keep on going. It's a basic law of physics (known as Newton's first law of motion, after brilliant English physicist Sir Isaac Newton who first stated it) that things that are moving tend to keep on moving until something (a force of some kind) stops them. Cars have had seat belts for decades, but they're a fairly crude form of protection. The biggest problem is that they restrain only your body. Your head weighs a surprising 3–6kg (6–12lb)—as much as several bags of sugar— and isn't restrained at all. So even if your body is fastened tight, the same basic law of physics says your head will keep on going and smash into the steering wheel or the glass windshield (windscreen). That's where airbags come
Photo: Sir Isaac Newton (1642–1727) formulated three basic laws describing how forces work. Picture courtesy of US Library of Congress.
The basic idea is that the airbag inflates as soon as the car starts to slow down in an accident and deflates as your head presses against it. That's important: if the bag didn't deflate, your head would just bounce back off it and you'd be no better off.
1) The crash sensors do not signal for the airbag to inflate unless the vehicle is moving at least 6 km/h. Damage can still occur to the passenger if the collision is of a slower speed. This is were the seat belt plays an important role.
2) The airbag located in the steering wheel does not help the passenger in a collision where another car hits them side on.
3) When the car the passenger is in is backing up and collides the its rear end with another object the airbag does not help.
With today's technology other airbags are being introduced in addition to the steering wheel airbag and the passenger airbag. Such airbags that are being introduced are side airbags and head airbags.
The trouble with momentum
Like everything else in the world, car crashes are controlled by the laws of physics—and, more specifically, the laws of motion. Anything that moves has mass (very loosely speaking, this means how much "stuff" an object contains and it's closely related to how heavy it feels) and velocity (loosely, this is the same thing as speed, but strictly it means speed in a certain direction). Anything that has mass and velocity has kinetic energy, and the heavier your car and the faster you're going, the more kinetic energy it has. That's fine until you suddenly want to stop—or until you crash into something. Then all the energy has to go somewhere. Even though cars are designed to crumple up and absorb impacts, their energy still poses a major risk to the driver and passengers.
The trouble is, people inside a moving car have mass and velocity too and, even if the car stops, they'll tend to keep on going. It's a basic law of physics (known as Newton's first law of motion, after brilliant English physicist Sir Isaac Newton who first stated it) that things that are moving tend to keep on moving until something (a force of some kind) stops them. Cars have had seat belts for decades, but they're a fairly crude form of protection. The biggest problem is that they restrain only your body. Your head weighs a surprising 3–6kg (6–12lb)—as much as several bags of sugar— and isn't restrained at all. So even if your body is fastened tight, the same basic law of physics says your head will keep on going and smash into the steering wheel or the glass windshield (windscreen). That's where airbags come
Photo: Sir Isaac Newton (1642–1727) formulated three basic laws describing how forces work. Picture courtesy of US Library of Congress.
How airbags help
An airbag is more correctly known as a supplementary restraint system (SRS) or supplementary inflatable restraint (SIR). The word "supplementary" here means that the airbag is designed to help the seatbelts protect you rather than replace them (relying on an airbag to protect you without fastening your seatbelt is extremely dangerous).The basic idea is that the airbag inflates as soon as the car starts to slow down in an accident and deflates as your head presses against it. That's important: if the bag didn't deflate, your head would just bounce back off it and you'd be no better off.
How airbags work
- When a car hits something, it starts to decelerate (lose speed) very rapidly.
- An accelerometer (electronic chip that measures acceleration or force) detects the change of speed.
- If the deceleration is great enough, the accelerometer triggers the airbag circuit. Normal braking doesn't generate enough force to do this.
- The airbag circuit passes an electric current through a heating element (a bit like one of the wires in a toaster).
- The heating element ignites a chemical explosive. Older airbags used sodium azide as their explosive; newer ones use different chemicals.
- As the explosive burns, it generates a massive amount of harmless gas (typically either nitrogen or argon) that floods into a nylon bag packed behind the steering wheel.
- As the bag expands, it blows the plastic cover off the steering wheel and inflates in front of the driver. The bag is coated with a chalky substance such as talcum powder to help it unwrap smoothly.
- The driver (moving forward because of the impact) pushes against the bag. This makes the bag deflate as the gas it contains escapes through small holes around its edges. By the time the car stops, the bag should have completely deflated.
uses : In cars specially
related link : https://www.youtube.com/watch?v=KZOdljBtoeo
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