Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Kinetic energy of N solid bodies

  1. May 13, 2010 #1

    Oddbio

    User Avatar
    Gold Member

    This is a fairly simple question so I wasn't sure if it belongs here, but it is not a homework question. Just a question on something I'm reading.

    The book says there are N solid bodies with initial speed vi (i=1, 2, 3, ..., N)
    and final speed vi' after some shock to the system.

    The book then says that the difference in kinetic energy is:
    [tex]\sum_{i=1}^{N}m_{i}(v_{i}'^{2}-v_{i}^{2})[/tex]

    But my question is, where did the (1/2) factor go from the kinetic energy?

    I was even wondering if this has something to do with combining the sum for initial and final kinetic energies into a single script, but if I write the sum out using "j" for initial and "i" for final in the sums it comes out to be what they have but with a (1/2)... like I think it should.
    Am I supposed to assume that this is just a typo? Even though several calculations are performed from that equation following its appearance.
    I can't see any reason why it would be missing.
     
  2. jcsd
  3. May 14, 2010 #2

    tiny-tim

    User Avatar
    Science Advisor
    Homework Helper

    Hi Oddbio! :smile:
    Typo (or laziness of the author)! :rolleyes:

    I assume that it makes no difference to the calculations because it's missing from both sides of every equation.

    But the author still shouldn't leave it out without warning. :frown:
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Kinetic energy of N solid bodies
  1. N body problem help (Replies: 1)

Loading...