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Homework Help: Percent of energy lost?

  1. Oct 31, 2006 #1
    percent of energy lost???

    I'm confused... I have a case where block 1 moves with certain velocity, hits block 2 (that is at rest) and sticks to it - inelastic collision. Now, the problem is that I have to find the percent of energy (kinetic) that the first block has lost. I know that the formula is [(K initial - K final)/K(initial)]*100, but wha I'm wandering about is whether K(final) should include the mass of block 2 or not?
    They are actually one mass after collision, but the question asks for the lost of energy of block 1. Can you somehow explain this to me? Thank you!
  2. jcsd
  3. Oct 31, 2006 #2
    Yeah, calculate the final kinetic energy with the combined mass.
  4. Oct 31, 2006 #3
    Thanks, I got it right!
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