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Electromagnetism help

  1. Nov 6, 2009 #1
    urgent electromagnetism help

    1. The problem statement, all variables and given/known data
    Assume that dust particle in the solar system are spherical, black and have a density of 2000kg/m^3. Use the total luminosity of the sun to calculate the time average poynting vector of the radiation at a distance r from the Sun. Hence estimate what is the maximum size of a dust particle that can be help in orbit by gravity around the sun without being blown away by radiation pressure.

    2. Relevant equations

    3. The attempt at a solution
    I have no idea about finding the poynting vector

    For the second bit do i use P=F/A and F=GMm/R^2, and P(radiation)=S/c?
  2. jcsd
  3. Nov 7, 2009 #2
    Re: urgent electromagnetism help

    If you use the luminosity equation I=P/A you don't need to work out the pointing vector. The P value from the previous equation will give you that.

    For your own info P=[HxE] is the Poynting vector.
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