PHYS 317 - Reading Assignment #1

Read sections 1.1-1.3, and answer the following questions by email (, hardcopy, or web form before class Friday, Aug 29.

  1. What is the relation (analogous to the ideal gas law) between the pressure and the average velocity?

    Eq. (1.14), P = N m < vx2 >, where <.> means ``average'' (I don't know how to make an overline in html). Equivalently, you could use the velocity instead of the x-component with P = N m < v2 > /3, where <.> means ``average''

  2. Is equation (1.20) true for non-ideal gasses?

    Yes, oddly enough. We'll learn why later.

  3. Does a diatomic molecule have a higher or lower thermal energy than a monatomic molecule?

    Higher. U = (5/2) N k T for a diatomic molecule (assuming the bond isn't oscillating) and U = (3/2) N k T for a monatomic molecule.

  4. What is the average thermal energy for a diatomic gas at very high temperatures (neglecting relativity)?

    When the bond begins to oscillate, which is usually much higher than room temperature, then there are 7 degrees of freedom instead of 5, so U = (7/2) N k T.

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