Force
Forces and Motion

The invention of the air bag

Stories from Physics for 11-14 14-16 IOP RESOURCES

The inventor of the air bag, John W Hetrick, attributes his invention to an accident that occurred when he was out a Sunday drive with his wife and young daughter in 1952. Hetrick swung his car into a ditch in order to avoid a deer, and he and his wife flung their hands up to protect their daughter. While driving home after the crash, he had the idea of an object coming out of the dashboard to soften a collision and began to develop sketches of his idea. His invention was further inspired by an accident he witnessed during the Second World War. While repairing a torpedo, the compressed air inside the weapon was accidentally released, firing the torpedo’s canvas cover to the ceiling. Hetrick’s original patent for the air bag used a spring-loaded mass as the trigger, probably would not have worked in practice, and he never earned any money from his invention. Most contemporary systems use nitrogen generated from the reaction between sodium azide, potassium nitrate and silicon dioxide in order to fill the airbag rapidly. The first recorded head-on collision in which both cars deployed airbags occurred in 1990 in Culpeper, Virginia — both drivers suffered only minor injuries.

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