1. Not finding help here? Sign up for a free 30min 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!

Spherical coordinates vector

  1. Oct 5, 2015 #1
    1. The problem statement, all variables and given/known data
    Find the vector directed from (10,3π/4,π/6) to (5, π/4,π), where the endpoints are given in spherical
    coordinates. Ans -9.660ax, - 3ay. + 10.61az

    2. Relevant equations
    az=rCosΦ

    3. The attempt at a solution
    az=10Cos(π/6) +5Cos(π) =13.6

    My answer differs. Where did i go wrong?
     
  2. jcsd
  3. Oct 5, 2015 #2

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Nice answer, but: how did you get it ? Please show the detailed steps you take.
     
  4. Oct 5, 2015 #3
    I'm not sure which answer you refer to. The answer is given in the book. I did only for z-axis in Cartesians coordinates. The answer from the book foe z-axis is 10.61 but my calculation, az=10Cos(π/6) +5Cos(π) =13.6
     
  5. Oct 5, 2015 #4

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    the only answer I see is the az. What did you do to get it ? (It looks to me you are adding z-coordinates)
     
  6. Oct 5, 2015 #5
    Spherical coordinates
    A= (10,3π/4,π/6)
    B= (5, π/4,π),

    X=rSinΦCosθ
    Y=rSinΦSinθ
    Z=rCosΦ
    Cartesian coordinates
    A=(-3.53, 3.53, 8.66)
    B=(0 ,0, -5)

    AB= B-A=(3.53, -3.53, -13.66)
     
  7. Oct 5, 2015 #6

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Ah, I see. Not only the z coordinate answer differs ! :wink:

    You assume you are given ##(r, \phi, \theta)##. The "usual" order may well be ##(r, \theta, \phi)##. Eureka !
     
  8. Oct 5, 2015 #7

    BvU

    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Turns out here is a set of two pictures that might explain why you and the book perceived differently !
     
  9. Oct 5, 2015 #8
    Thank you. Get the answer and know where's the error.
     
  10. Oct 5, 2015 #9

    Ray Vickson

    User Avatar
    Science Advisor
    Homework Helper

    Be careful: there are two common versions of spherical coordinates: see, eg., https://en.wikipedia.org/wiki/Spherical_coordinate_system . Which convention does your problem use?

    Note added in edit: again, many of the replies did not appear on my screen until after I posted the current message. Posts # 6,7,8 were unavailable to me until after I hit the "enter" key. That keeps happening. Does anyone know why?
     
    Last edited: Oct 5, 2015
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Spherical coordinates vector
  1. Spherical Coordinates (Replies: 2)

Loading...