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Homework Help: The percentage and force of Friction ( 9/28/09)

  1. Sep 28, 2009 #1
    1. The problem statement, all variables and given/known data

    Hi everyone,

    I have 2 quick Questions, about my HW so if u think u can give me a hit plz post.

    2. Relevant equations

    the Question was :-

    10g bullet is fired into a ballistic pendulum made from a 4kg wood block and two light cords. The block's vertical displeacment is 5 cm.


    what is the inital velocity.

    what percentage of the bullet's initial kinetic energy is lost in the collision

    what is the force of friction acting on the bullet in the block assuming that it stops in 3 cm

    3. The attempt at a solution

    I found the initial velocity in to the equation

    1/2mv^2 = mgh

    and i got 19.8 m/s

    so plz help me with 2nd and the 3rd Qs
  2. jcsd
  3. Sep 28, 2009 #2
    k i got for the 3ed Q


    I used the equation

    F= ma
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