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Homework Help: Force of Air-bag deployment.

  1. Oct 30, 2007 #1
    1. The problem statement, all variables and given/known data
    Maximum acceleration during a car crash should not exceed 60 g's and should not last more than 36 ms. Find force of air-bag on an 89 kg person.

    2. Relevant equations

    I was given no equations.

    3. The attempt at a solution

    I just need the equation really!
  2. jcsd
  3. Oct 30, 2007 #2
    Well, the equation for this is F=m*a.

    The accelleration should then be the equivalent of 60g's (if that is what the problem is suggesting), and the mass equal to 89 kg. I'm not sure why you would need the time of the crash, but generally, the force would then be:


    However, this is only if the body is taking the full force. Basically, there is no resistance from the driver, and the airbag does not decrease the accelleration.

    I hope I helped, the question was fairly vague, please add an attempt next time.
  4. Oct 30, 2007 #3
    Okay, my homework is submitted online, and that is exactly what I did and it told me I was wrong. I didn't put any attempts because I thought they were horribly wrong because I did F=m*a and it didn't work. But that's what I originally got. And yes, my homework questions are horribly vague. I've been working on this problem since last night!
  5. Oct 30, 2007 #4
    If that is what you originally got, then why didn't you put up your attempt?
  6. Oct 30, 2007 #5
    Because when I submitted it to my homework website it told me I was wrong, so I figured I was doing the wrong thing.
  7. Oct 30, 2007 #6
    Well, what we generally do is you add your attempt and we look for what was wrong with it. It is harder to go off of a singular problem when we do not know what section in physics you are specifically studying. A problem like that could be attributed to other physics such as thermodynamics and the rising heat from the airbag.

    However: Just in case, have you checked whether you are entering the correct sigfigs? Sometimes those trip up people who arn't ready for the computer to be sentitive about them.
    Last edited: Oct 30, 2007
  8. Oct 30, 2007 #7
    I apologize. I think it may be an error with the website rather than being unable to figure it out. It's a very simple force problem, it's not meant to have any other particular fields involved.
  9. Oct 30, 2007 #8
    Alright, I figured out the bug, the website was being finicky about the significant figures.

    I now need to express the force in terms of the persons weight. I have no idea what that means.
  10. Oct 31, 2007 #9
    I think it is implying that it wants you to give the equation for the force with the person's weight as a variable.
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