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Homework Help: Impulse Question

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

    A bullet with a mass of 0.005 kg and moving with a speed of 400 m/s penetrates a distance of 0.08m into a wooden block firmly attached to the Earth. Assume that the force stops it is constant. Compute for:

    a.) acceleration of the bullet
    b.) accelerating force
    c.) time of acceleration
    d.) impulse of the bullet

    2. Relevant equations

    I think I'll use

    a=-Vi^2 / 2s.

    for the acceleration of the bullet.

    then for the acceleration of the bullet,


    then for the time of acceleration,

    t = m(Vf-Vi) / F

    am i right?
  2. jcsd
  3. Jan 20, 2009 #2


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    Gold Member

    No, what is Newton's second law?
    yes, (or use t = (Vf -Vi)/a , as a check)
    and part d?
  4. Jan 21, 2009 #3
    a.) acceleration of the bullet = 1,000,000 m/s^2
    b.) accelerating force = 5000N
    c.) time of acceleration = 0.0004 s
    d.) impulse of the bullet = 2 Ns

    are these correct? I used the equations above. I'm in doubt whether this is correct because of those large numbers and for that small amount of time.

    I used the equation of I=Ft for impulse.
    Last edited: Jan 21, 2009
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