Explain why airbags have become common safety mechanisms in

Explain why airbags have become common safety mechanisms in automobiles. Consider in particular the forces between a passenger and an airbag, or passenger and seatbelt. Show your reasoning with words, diagrams, and/or mathematics. Use dynamics principles to support your design, and make engineering estimates when necessary - that is, make up reasonable numbers.

Solution

Considering the laws of motion:

First, we know that moving objects have momentum (the product of the mass and the velocity of an object; F=ma, inertia force). Unless an outside force acts on an object, the object will continue to move at its present speed and direction. Cars consist of several objects, including the vehicle itself, loose objects in the car and, of course, passengers. If these objects are not restrained, they will continue moving at whatever speed the car is travelling at, even if the car is stopped by a collision.

Stopping an object\'s momentum requires force acting over a period of time. When a car crashes, the force required to stop an object is very great because the car\'s momentum has changed instantly while the passengers\' has not. There is not much time to work with. The goal of any supplemental restraint system is to help stop the passenger while doing as little damage to him or her as possible.

Airbag slows the passenger\'s speed to zero with little or no damage. The constraints that it has to work within are huge. The airbag has the space between the passenger and the steering wheel or dashboard and a fraction of a second to work with.

On the other hand, a seat belt stops the passenger abruptly giving him/her a shock which is undesirable on the passenger\'s end. This is the reason that airbags have gained such popularity in the market.

Dynamics behind the working:

A 2.5-cubic-foot driver’s front airbag inflates in as little as 20 to 30 milliseconds. Hurtling forward at 30 mph, an unbelted driver moves through the space between his chest and the wheel in 23 or so milliseconds. Since there’s more space between the passenger and the dashboard, that airbag has a larger volume and takes more time to fill.

This time duration is sufficient to avoid the consequences of a crash.

For example:

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.

I hope the working along with the dynamics of the airbag is clear.