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Homework Help: Wood block collision

  1. Feb 5, 2004 #1
    I need help with this problem. I dont know what equation to use.

    A 5.5g bullet is fired into a block of wood w/a mass of 22.6g.
    The wood block is initially at rest on a 1.5m tall post. After
    the collision, the wood block and bullet land 2.5m from the base of the post. What is the initial speed of the bullet?

    I tried to do this myself but all I got was the givens, I had no idea of where to start!
  2. jcsd
  3. Feb 5, 2004 #2


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    Staff Emeritus
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    Step 1: Use Newtonian mechanics to figure out how fast the block+bullet had to be moving horizontally to go 2.5 m in the time it took to fall 1.5 m.

    Step 2: Use the conservation of linear momentum in a completely inelastic collision to find the initial speed of the bullet.

    - Warren
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