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Net Force and Deacceleration

  1. Oct 24, 2009 #1
    1. The problem statement, all variables and given/known data

    A 58 kg person is in a head-on collision. The car's speed at impact is 13 m/s. Estimate the net force on the person if he or she is wearing a seat belt and if the air bag deploys.

    For some reason, I can't seem to get the correct answer to this question... I have no idea where I am going wrong. According to the question, if a person is wearing a seatbelt, they deaccelerate over a distance of 1m.

    2. Relevant equations

    (Final Velocity)^2 = (Initial Velocity)^2 + 2*acceleration*distance
    Force=mass*acceleration

    3. The attempt at a solution

    First off, I had to find the deacceleration over the distance of 1m:
    (Final Velocity)^2 = (Initial Velocity)^2 + 2*acceleration*distance
    0 = (13m/s)^2 + 2*acceleration*1m
    acceleration= -84.5m/s^2

    Using that acceleration to calculate net force...
    F=ma
    = (58kg)(-84.5m/s^2)
    =-4901N

    I put that answer into the system and it comes back wrong...

    Help is appreciated. Thanks!
     
  2. jcsd
  3. Oct 25, 2009 #2
    well it sound reasonable to me
    but thinking back if a person wearing seatbelt should they move forward then move back ward?
     
  4. Oct 25, 2009 #3
    Don't forget about your significant figures.
     
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