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Homework Help: What should I do next?

  1. Nov 7, 2004 #1
    the original problem:
    A 0.010-kg bullet traveling horizontally at 400.0 m/s strikes a 4.0-kg block of wood sitting at the edge of a table. The bullet is lodged into the wood. If the table height is 1.2 m, how far from the table does the block hit the floor?

    this is what i did:

    lets the mass of bullet = m2
    the mass of block of wood = m1
    velocity of the block of wood before the collision take place = v1
    velocity of the bullet = v2
    velocity of the block and bullet after the collision take place = vf
    momenta of the block = p1
    momenta of the bullet = p2

    the momentum of block and bullet after collision equals the sum of momenta of the block and the bullet before the collision:

    pf = pi

    The initial momentum is the sum of the momenta of the block and bullet

    pf = p1 + p2

    Since the block is initially at rest, p1 = 0. Then

    pf = p2
    or
    (m1 + m2)(vf) = (m2)(v2)

    Solving for vf:

    vf = [(0.010)(400.0)]/(4.0+0.010) = 0.9975 m/s

    And I stuck here because I didn't know how to calculate the distance from the table to the point that the block hit the floor.
    Am I have to use the projectile motion concept?
    Your help would be highly appreciate.
     
  2. jcsd
  3. Nov 7, 2004 #2
    Yes, you have to use the projectile motion formulas.
     
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