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Force Needed to Stop a Flying Bullet

  1. Nov 20, 2011 #1
    A bullet of mass 0.0025 kg moving at 470 m/s
    impacts a large fixed block of wood and travels
    6.2 cm before coming to rest.
    Assuming that the deceleration of the bullet
    is constant, find the force exerted by the wood
    on the bullet.
    Answer in units of kN

    I know force= mass * acceleration but i don't know how the distance plays into the solution. Any kind of kinematics formula would be sufficiently helpful!
     
  2. jcsd
  3. Nov 20, 2011 #2

    PeterO

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    Homework Helper

    Choose wisely from the sets of equations shown in the first two sections of this wikipedia posting.

    http://en.wikipedia.org/wiki/Equations_of_motion
     
  4. Nov 20, 2011 #3
    i was trying to use v^2= u^2+2as
    but the answer i am getting is wrong....
    is there a different formula you suggest?
     
  5. Nov 20, 2011 #4

    PeterO

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    Homework Helper

    That is certainly the one I would use.

    Were you converting everything to metres and seconds?

    This formula will only calculate the acceleration of course - you need at least one more step to get the force.
     
  6. Nov 20, 2011 #5
    nevermind. i was not converting my answer into kN.... thank you so much!
     
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