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Homework Help: Average force to keep something in place during an automobile crash?

  1. Dec 11, 2012 #1
    1. The problem statement, all variables and given/known data

    Suppose that a seat-belted mother riding in an automobile holds a 10 kg baby in her arms. the automobile crashes and decelerates from 50km/h to 0 in .1 s. what average force would the mother have to exert on the baby to hold it?? do you think she can do this?

    2. Relevant equations

    3. The attempt at a solution

    I think that you would use the elastic collision equation to solve this but i'm not entirely sure... i'm not very good at solving problems where you convert different equations into something else.
  2. jcsd
  3. Dec 12, 2012 #2
    Have you learned about Impulse yet (change in momentum)?

    What is force a product of? What's given to you in this problem? Focus on the baby rather than the car's collision, you aren't given any information about the object that the car collides with.
    Last edited: Dec 12, 2012
  4. Dec 12, 2012 #3
    You can use Newton's second law to solve this problem Katie.
  5. Dec 12, 2012 #4
    You can use Newton's second law to solve this problem Katie.
  6. Dec 12, 2012 #5


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    The problem statement gives an initial velocity U for the baby. You would hope that after time t the final velocity V is zero (otherwise the car will have stopped but baby is still moving and will impact the dash). So you have enough info to work out the deceleration required.

    If the mass and deceleration are known you can calculate the force required to achieve it.
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