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Homework Help: 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


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    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


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    Homework Helper

    Correct :smile:

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