1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    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!

Homework Help: Special Relativistic force problem.

  1. Oct 9, 2012 #1
    1. The problem statement, all variables and given/known data

    At the radius of the Earth’s orbit around the sun ([itex]1.5 *10^13[/itex]cm = 1AU), the flux of radiation from the sun is [itex] 10^6 erg/
    cm^2·sec[/itex] . Now consider a spherical dust grain of radius r with internal density
    [itex]\rho = 2g/cm^3[/itex], at some distance R from the sun. Assume that the grain is at rest with respect to the sun. Use the fact that radiation flux falls with distance from a source as 1/R2 Ignore the gravity of the Earth in this problem, but not the gravity of the Sun. Use Newtonian gravity and ignore general relativistic

    2. Relevant equations

    I won't both writing them out but we can easily derive the force from the flux & gravity effects on the particle.

    Now here is where things get a bit sticky for me. I want to just set these forces equal and solve as per the usual, but I am assuming that the problem must be trickier than that considering this an upper level course.

    My teacher suggested that we set both equal to the 3-vector momentum and go from there, but I derived the same results doing this as I did just setting the two equations equal.

    Where am I going wrong here? Or am I solving this the correct way?
  2. jcsd
  3. Oct 10, 2012 #2

    rude man

    User Avatar
    Homework Helper
    Gold Member

    And the problem is .... ?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook