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Collisions in One Dimension

  1. Oct 9, 2011 #1
    1. The problem statement, all variables and given/known data
    A 10.0g bullet is fired into a stationary block of wood (m=5.00 kg). The bullet imbeds into the block. The speed of the bullet-plus-wood combination immediately after the collision is 0.600 m/s. What was the original speed of the bullet?

    ball m=10.0g=0.01kg
    wood m= 5.00kg
    Vf=0.600m/s
    Vi=?


    2. Relevant equations
    p=mv


    3. The attempt at a solution
    i=change in momentum
    =mVi-mVf
    So, solve for Vi?
    Then I would have to know what i is, right?

    Thank you.
     
  2. jcsd
  3. Oct 9, 2011 #2

    gneill

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    Staff: Mentor

    Write equations for the momentum before and after the collision takes place. Be sure to specify which masses are involved.
     
  4. Oct 10, 2011 #3
    p=mv
    The momentum found using final velocity:
    p=(0.01kg)(0.600m/s)=0.006 kg*m/s (ball)
    p=(5.00kg)(0.600m/s)=0.006 kg*m/s (wood)
    And I assumed the initial velocity was zero, so I ended up with a zero momentum.
    Is that correct so far?
     
  5. Oct 10, 2011 #4

    lightgrav

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    Homework Helper

    no, the bullet started with (fast) unknown velocity
    It was theonly thing that HAD momentum, at first.
     
  6. Oct 15, 2011 #5
    Thanks, I finally figured it out. :D
     
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