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Homework Help: Collisions - bullet shot in in block

  1. Jun 7, 2014 #1
    Three blocks (1,2,3) of mass 3.00 kg, 2.00 kg, 1.00 kg sit
    linearly 10.0 cm apart from each other on a frictionless surface.
    A 25 g bullet is shot at the first block, it travels through the first
    block, and embeds itself into the second block (without falling over) which then collides into the
    third block.
    a. Assuming the final collision is elastic, and the third block has a final velocity of 5.00 m/s, what is
    the velocity of block 2 just before it collides into block 3?
    b. What is the velocity of the bullet before it embeds itself into block 2?
    c. Assuming the bullet slowed down by only 10% while it travelled through block 1, what was the
    speed of block 1 after the bullet traveled through it?
    d. What percent of the initial energy of the bullet was lost?

    I tried using the formula (2m1/m2+m2)* v1 for all the question in the problem. But the numbers don't sound right to me.
    Last edited: Jun 7, 2014
  2. jcsd
  3. Jun 7, 2014 #2


    User Avatar
    2017 Award

    Staff: Mentor

    Please show your calculations and numbers then. Otherwise we have no way to tell what went wrong. Your formula looks a bit odd, but that could be a typo.

    Note that some collisions are not elastic.
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