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Homework Help: Bullet passing through 4cm thick board

  1. Feb 24, 2008 #1
    1. The problem statement, all variables and given/known data

    A bullet traveling horizontally at a speed of 350 m/s hits a board perpendicular to the surface, passes through it, and it emerges on the other side at a speed of 210 m/s. If the board is 4 cm thick, how long does the bullet take to pass through it (in seconds)?

    2. Relevant equations

    X(t) = Vt + x(i)

    3. The attempt at a solution

    My problem is not knowing which formula to use. Thank you
  2. jcsd
  3. Feb 24, 2008 #2
    if you consider that the acceleration of the bullet is constant in the board. than, i think you can handle it.
  4. Feb 24, 2008 #3
    First off, deceleration is constant, if the board is uniform.
    The equation you use is d=.5(vo+vf)t. d, vo, vf is given. Also, don't forget to convert cm to m.
  5. Feb 24, 2008 #4
    Thank you very much, Silvashadow
  6. Feb 24, 2008 #5
    Did I get it right?
  7. Feb 24, 2008 #6
    Yes, I got it right! In the future I will remember to mention that.

    Also, would you please see my other thread (titled “angle of bullet when fired”) and let me know if I am on the right track for answering the question.

    FYI, there is no additional information to the problem (titled “angle of bullet when fired”), other than what was stated. Thank you

    The possible answers for the problem (titled “angle of bullet when fired”), are 3, 10, 30 and 80.
  8. Oct 1, 2009 #7
    Ive been looking at this problem for a few minutes.
    What does the d stand for in the forumla that silvashadow mentions?

    i get that d=.5(350+210)t where t is what we are looking for. is d 4?
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