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Homework Help: Different kinds of Kinetic energy

  1. May 12, 2007 #1
    I'm studying thermodynamics and I've come across different types of KE's in the motion of molecules within gases. What is "translational kinetic energy?" Is "rotational kinetic energy" just the rotational movement of the molecules?
  2. jcsd
  3. May 12, 2007 #2
    "Kinetic energy is the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy. There are many forms of kinetic energy - vibrational (the energy due to vibrational motion), rotational (the energy due to rotational motion), and translational (the energy due to motion from one location to another)."

    You can find that information anywhere on the internet. Just search Google.
  4. May 12, 2007 #3
    oh okay. I just didn't know what the word "translational" meant. Also, are the internal energy and avg KE both equal to: [tex]\frac{3}{2}k_{b}T[/tex]?? Is this true because the internal energy is basically all of the KE and PE's of molecules within the system? I'm referring to the avg KE and internal energy per molecule and not the total KE and internal energy
  5. May 12, 2007 #4
    I'm kind of getting confused on moles, molecules, molar mass, mass of the molecules. Does anyone mind making these terms more clearer to me? I can only figure their meanings through equations and even if I do I still don't know their real meanings.

    [tex]n=\frac{N}{N_{A}} \qquad m*N_{A}=M[/tex]

    I especially don't get the molar mass equation, here is what I did to somewhat get a sense of the meanings:

    [tex] [\frac{mass}{#molecules}*\frac{#molecules}{mole}=\frac{mass}{mole}][/tex]

    m is the mass of all of the molecules correct? Which would also be equal to the total weight of the gas??
  6. May 12, 2007 #5
    I'm reading my text and it seems like [tex] KE=\Delta U=W [/tex] can these three variables be used interchangably but not conceptually? I keep getting mixed up with these three and would like to know if they are always equal to each other. I know that U relates to the microscopic molecular energies of the system so their units are all the same but..
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