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Homework Help: Finding the force required to stop an object

  1. Sep 11, 2011 #1
    1. The problem statement, all variables and given/known data
    An object with mass [itex]6.9*10^-3 kg[/itex] and velocity 1300 m/s comes to a stop in 1cm. What force was applied to stop it?

    2. Relevant equations
    F = ma
    [itex]v^2=v_o ^2+2a\Delta x[/itex]

    3. The attempt at a solution
    [itex]v^2=v_o ^2+2a\Delta x[/itex]
    [itex]a=-\frac{(1300)^2}{2(0.001)}=-8.45*10^8 \frac{m}{s^2}[/itex]

    [itex]F=(6.9*10^{-3} kg)(-8.45*10^8 \frac{m}{s^2})= -5.83*10^6 N[/itex]

    Apparently that is not the correct answer. What did I do wrong?

    Many thanks!
    Last edited: Sep 11, 2011
  2. jcsd
  3. Sep 11, 2011 #2


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    Science Advisor
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    Gold Member

    1 cm = 0.01 m not 0.001 m.
  4. Sep 11, 2011 #3
    Well now, I feel kind of silly :) At least it was a good mistake to make, being so simple to fix!

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