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Homework Help: Kinetic energy

  1. Dec 28, 2004 #1
    Not understanding a formula for this problem

    Which has more kinectic energy a .00020-kg bullet traveling at 400m/s or a 6.4 10 to 7th power -kg ocean liner traveling at 10m/s (20 knots)?

    I know that w=fd=mad=ma(1/2)at2) =1/2m(at)2 +1/2mv2 Is this the right formula?
  2. jcsd
  3. Dec 28, 2004 #2
    KE = (1/2)mv^2. Use that to work out the KE for the bullet and the ocean liner, then compare them.
  4. Dec 28, 2004 #3

    Andrew Mason

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    Homework Helper

    You can just look at this and see that the ocean liner has much more kinetic energy. It is comparing the energy of .bb gun to the Titanic at full speed! So it isn't a great question. How about a highpowered rifle bullet and a more modest ship moving at a more modest speed :

    a 20 gram (.02 kg) bullet at 1000 m/sec, and a 1,500 Tonne ship at 10 cm/sec

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