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A bullet, having a mass of 18g and traveling with a velocity of 1200 m/s strikies a

  1. Nov 25, 2007 #1
    1. The problem statement, all variables and given/known data

    A bullet, having a mass of 18g and traveling with a velocity of 1200 m/s strikies a wooden block and pentrates 2.5m. What is the average force exerted by the block on the bullet?


    2. Relevant equations

    W= F*total distance
    W= .5*m*V2^2 - .5*m*V1^2

    3. The attempt at a solution

    i got the answer -12960 J
     
  2. jcsd
  3. Nov 25, 2007 #2

    rock.freak667

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    Homework Helper

    The question is
    Now your answer is in Joules..Force is in Newtons...so you missed something

    Consider the law of conservation of energy;
    The Kinetic energy lost by the bullet= Work done in moving the bullet 2.5m into the wooden block....
    [tex]E_k=W[/tex]

    now you know [itex]E_k=\frac{1}{2}mv^2[/itex] and you know [itex]W=Fs[/itex]
    so you can find F
     
  4. Nov 25, 2007 #3
    em i still don't think i have the right answer 43200 is that right
     
  5. Nov 25, 2007 #4

    rock.freak667

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    Homework Helper

    [tex]\frac{1}{2}*\frac{18}{1000}*1200^2=F*2.5[/tex]
    And so
    [tex]12960=2.5F =>F=5184N[/tex]
     
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