FREE ESSAY ON AIRBAGS

AIRBAGS

Air bags have been used in automobiles since the 1980s. The trend gathered momentum in the
early and mid 1990s, during which major car manufacturers repeatedly boasted putting
airbags in their new models for the driver. Beginning in 1998, driver- and passenger-side
air bags have been required by law for all new cars in the United States. The air bag,
however, was not born in a design room at the Ford Motor Company. The first inflatable
device patented to help prevent injuries from crashes actually appeared in airplanes
during World War II.
Studies have shown that air bags help reduce the risk of death from a direct frontal
crash by about 30 percent. Newer, yet not so widely used, are seat- and door-mounted side
air bags, which are credited with reducing death and injury rates from side collisions.
An air bag works by stopping the continuing motion of a body within a car, while the car
itself has stopped instantly. In theory, this seems to be a rather simple task. The
frailty of the human body, however, makes this task one of precision sensitivity.
The first problem with which the air bag must contend is the relatively small space
between the passenger and the steering wheel (or dashboard). A body moving at 100, or
even 40, kilometers per hour only has about 0.3 meters to come to a stop. The second
problem is the fraction of a second that the body has to come to this stop. The final
problem is absorbing or cradling the force of the body, rather than stopping it
abruptly.
Sensors cause a bag to deploy during a crash if the force is equal to or greater than the
force of running into a brick wall at about 17 kph. A mechanical switch inside the car
closes due to a shift in mass and an electrical contact is made.
The critical window of prevention is only about 1/25 of a second. The bag must burst from
its shell at about 340 kph in order to be effective in a crash. This is accomplished by
the reaction of sodium azide and potassium nitrate, which produces hot nitrogen gas to
inflate the bag. To solve the problem of cradling, rather than outright stopping, the air
bag is made of porous nylon, which begins to deflate 1 second after deployment. This
deflation not only causes a cradling effect, but also prevents the passenger from being
trapped in that small space between the seat and the dashboard.