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How does an air bag work?

  1. Jan 27, 2004 #1

    How does an air bag work?

    I know alot about how an air bag work as I am a physics grade11 student but I am confused how to really answer the question.Should I answer it techanically or use newtons law to answer it.

    Thanks in advance.
    An early reply is appreciated.
  2. jcsd
  3. Jan 27, 2004 #2

    There are three parts to an air bag. First, there is the bag itself, which is made of thin, nylon fabric and folded into the steering wheel or the dash board. Then there is the sensor that tells the bag to inflate. It detects a collision force equal to running into a brick wall at 10 to 15 miles per hour (16 to 24 kph).

    Finally, there is the inflation system. Air bags are actually inflated by the equivalent of a solid rocket booster. Sodium azide (NaN3) and potassium nitrate (KNO3) react very quickly to produce a large pulse of hot nitrogen gas. This gas inflates the bag, which literally bursts out of the steering wheel or dashboard as it expands. About a second later, the bag is already deflating (it has holes in it) in order to get out of your way.

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  4. Jan 27, 2004 #3


    how should I answer the question as my teacher is not actually teaching us all that about the air bag but gave us this question.
    We are learning about newtons laws.
  5. Jan 27, 2004 #4

    Doc Al

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    Staff: Mentor

    Re: thanks

    Try this line of reasoning: When you crash, your speed is changing from X miles per hour to zero. Thus you are being accelerated, which means a force is being applied to you. Without the airbag, you smack into the dashboard which brings you to a stop rather quickly---high acceleration, high force: not good! The airbag slows your acceleration---lower acceleration, lower force: good!

    Make some sense?
  6. Jan 27, 2004 #5
    Thanks so much for your help.
  7. Jan 28, 2004 #6


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    Homework Helper

    Same impulse; different maximum force.
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