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Homework Help: Coefficient of friction - bullet traveling through a block

  1. Mar 30, 2010 #1
    1. The problem statement, all variables and given/known data

    A bullet with a mass of 7.00 g is fired horizontally with a speed of 420 m/s, into a wooden block with mass of 0.820 kg, initially at rest on a level surface. The bullet passes through the block and emerges with its speed reduced to 130 m/s. The block slides a distance of 47.0 cm along the surface from its initial position.

    What is the coefficient of kinetic friction between block and surface?

    2. Relevant equations

    vf2=vi2+2ad

    F=ma

    uk = fk/n

    3. The attempt at a solution

    I found the acceleration of the bullet

    1302=4202+2a(.47)

    a= -169680.8

    i then thought i could find the force and then divide that by the normal force to get uk but my number was very large (141) :(

    Can anyone help me on this one please.

    Thank you :)
     
  2. jcsd
  3. Mar 30, 2010 #2

    Filip Larsen

    User Avatar
    Gold Member

    Think about if you perhaps can use conservation of momentum to analyze your problem.
     
  4. Mar 30, 2010 #3
    Got it. That worked perfectly. Thank you i appreciate it :)
     
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