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Vector distribution

  1. Dec 4, 2015 #1
    1. The problem statement, all variables and given/known data

    problems_MIT_RELATE_htmlwiki_Unit8_Module3_files_SpaceShuttleSol.png

    2. Relevant equations

    I know that
    ##F_g=(G*m_e*m)/r^2)##
    ##dr⃗ =drr_1+rdθθ_1.##

    ##F⃗ g⋅dr⃗ =−(Gm_em/r^2)*r_1⋅(drr_1+rdθθ_1)##

    ##F⃗ g⋅dr⃗ =−(Gm_em/r^2)(drr_1⋅r_1+r*dr*dθ*θ_1⋅r_1)##

    3. The attempt at a solution

    I don't understand why there is a dr in the 2nd term in the second bracket.
    I have used r_1 and ##theta_1## for unit vectors.
    I know how to proceed from this step (##r_1.r_1=1## whereas ##theta_1.r_1=0(perpendicular)##
     
    Last edited: Dec 4, 2015
  2. jcsd
  3. Dec 5, 2015 #2

    andrewkirk

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    There should not be a ##dr## there. It looks like a mistake.
    In any case it doesn't matter, as the term is zero because the dot product is.
     
  4. Dec 6, 2015 #3
    yes as unit vector θ and unit vector r are perpendicular .
    thanks.
     
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