Final answer:
Airbags always fill evenly to reduce the force on vehicle occupants during a crash, protecting them from serious injuries.
Step-by-step explanation:
Airbags always fill evenly because they are designed to reduce the force on vehicle occupants in a crash. When an impact occurs, a reaction is triggered that rapidly produces nitrogen gas, filling the airbag. The force of the impact is spread out over a larger surface area and a longer time, which reduces the force exerted on the occupants and minimizes serious injuries.
For example, when a car comes to a sudden stop, the momentum change experienced by the occupants is the same whether an airbag is deployed or not. However, if the force acts over a larger time, as it does with an airbag, the force will be much less and the occupants will be better protected.