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Homework Help: Finding force(N) wood has against the bullet

  1. Oct 1, 2011 #1
    1. The problem statement, all variables and given/known data

    22.0-caliber rifle bullet of mass 1.80 g, traveling at 320 m/s strikes a block of soft wood, which it penetrates to a depth of 0.140 m. The block of wood is clamped in place and doesn't move. Assume a constant retarding force.

    What force, in newtons, does the wood exert on the bullet?


    2. Relevant equations



    3. The attempt at a solution


    Long story short, acceleration is -365714.29 m/s^2

    Is it really as simple as .0018*-365714.29 = -658.29 N ? Or maybe 658.29 N since the force of the wood on the bullet is opposite of the bullet on the wood?

    Since Fnet = ma
     
    Last edited: Oct 1, 2011
  2. jcsd
  3. Oct 1, 2011 #2

    PeterO

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    It is that simple [I hope you a value is correct; I haven't checked]

    The question referred to a retarding force, so easiest just to answer "The retarding force is 658N" watch the significant figures in your final answer - you use all the figures i your calculations]
     
  4. Oct 1, 2011 #3

    Andrew Mason

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    You might find it easier to use energy: the work done by the wood on the bullet is equal to the loss of kinetic energy. So:

    [tex]F = KE/d[/tex]

    AM
     
  5. Oct 1, 2011 #4
    Thanks.
     
  6. Oct 1, 2011 #5
    Never thought about that! thanks, that would make it easier.
     
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