1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The virial theorem

  1. Jul 3, 2014 #1
    1. The problem statement, all variables and given/known data
    In the Virial theorem The scalar virial G is defined by the equation:
    $$G=\vec{p}\cdot \vec{r}$$
    Where ##\vec{p}## is the momentum vector and ##\vec{r}## the location vector.
    When i take the mean of the derivative ##\bar{\dot{G}}## over a whole period T it equals 0. why?

    2. Relevant equations
    $$\vec{p}\cdot \vec{r}=(mv)\cdot \cos \theta \cdot r$$

    3. The attempt at a solution
    I understand this scalar product is zeroed during one period, but why?
  2. jcsd
  3. Jul 4, 2014 #2


    User Avatar
    Homework Helper

    You said the function G is periodic. You want the mean of its time-derivative.

    How do you calculate the mean of a function?

    What is the integral of the derivative?

  4. Jul 4, 2014 #3
    I think i understand.
    Because the end point and the start point are identical G(T)=G(0)
  5. Jul 4, 2014 #4


    User Avatar
    Homework Helper

    Correct :smile:

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted