Airbags exist to minimize the force exerted on a person when a car crashes. Newton's 1st law tells us that an object is motion will stay in motion, so when you are riding in a car you are moving at the same direction and speed as the car. All moving objects have momentum which is equal to mass times velocity. In an effort to combat injury, cars now have to have airbags according to the federal law. Airbags work because they want to exert a force that will decrease the person in the car's speed to zero. The airbag extends the amount of time and retrains the person in the car in order to limit injury when involved in a crash because force equals mass times acceleration. When the time taken to slow a person's speed from high to low, the acceleration decreases and therefore the force of the car is less.