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Homework Help: Time of Bullet

  1. May 20, 2009 #1
    1. The problem statement, all variables and given/known data

    A rifle with a barrel length of 50.86 cm fires a 7.06 g bullet with a horizontal speed of 449 m/s. The bullet strikes a block of wood and penetrates to a depth of 12.9 cm.

    What resistive force (assumed to be constant) does the wood exert on the bullet?
    5516.6785 N

    3. The attempt at a solution

    How long does it take the bullet to come to rest?
    Shouldn't it just be t = v/a t = 449/ 5516.6785 = 8.14*10-2
    Thats what I'm getting but its saying im wrong... Am I missing something?
  2. jcsd
  3. May 20, 2009 #2
    F = ma

    Wood exerts 5516.6785 on the bullet like you said, work out the bullets deceleration then try SUVAT
  4. May 20, 2009 #3


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    Homework Helper

    You found the force by figuring the acceleration.

    t = v/a

    That's true. But unfortunately it's not = v / F
  5. May 20, 2009 #4
    WoW the rifle is too big. LOL
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