How to find the vector between two points given in spherical coordinates?

Or is it happening to anyone else?)xyz coordinatesProbably because you have the correct answer in Spherical coordinates. However, the question is asking for the vector in Cartesian coordinates, so the answer should be - 5ax - 3ay + 10.61az.
  • #1
azizlwl
1,066
10

Homework Statement


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

Homework Equations


az=rCosΦ

The Attempt at a Solution


az=10Cos(π/6) +5Cos(π) =13.6

My answer differs. Where did i go wrong?
 
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  • #2
Nice answer, but: how did you get it ? Please show the detailed steps you take.
 
  • #3
BvU said:
Nice answer, but: how did you get it ? Please show the detailed steps you take.

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
 
  • #4
I'm not sure which answer you refer to
the only answer I see is the az. What did you do to get it ? (It looks to me you are adding z-coordinates)
 
  • #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)
 
  • #6
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 !
 
  • #7
Turns out here is a set of two pictures that might explain why you and the book perceived differently !
 
  • Like
Likes azizlwl
  • #8
BvU said:
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 !
Thank you. Get the answer and know where's the error.
 
  • #9
azizlwl said:

Homework Statement


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

Homework Equations


az=rCosΦ

The Attempt at a Solution


az=10Cos(π/6) +5Cos(π) =13.6

My answer differs. Where did i go wrong?

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:

1. What are spherical coordinates vectors?

Spherical coordinates vectors are a system of representing points in three-dimensional space using three parameters: radius, inclination, and azimuth. In this system, a point is located by measuring the distance from the origin (radius), the angle between the positive z-axis and the line connecting the point to the origin (inclination), and the angle between the positive x-axis and the projection of the point onto the xy-plane (azimuth).

2. How are spherical coordinates vectors different from Cartesian coordinates?

Unlike Cartesian coordinates which use x, y, and z coordinates to represent a point, spherical coordinates use radius, inclination, and azimuth angles. This makes it easier to represent points that are located at a distance from the origin or are located on a curved surface.

3. What are the advantages of using spherical coordinates vectors?

One advantage of using spherical coordinates is that it simplifies the representation of points on a spherical or curved surface. It is also useful in physics and engineering applications, such as modeling the movement of objects in space.

4. How can I convert between spherical coordinates and Cartesian coordinates?

To convert from spherical coordinates to Cartesian coordinates, you can use the formulas x = r sin θ cos φ, y = r sin θ sin φ, and z = r cos θ, where r is the radius, θ is the inclination angle, and φ is the azimuth angle. To convert from Cartesian coordinates to spherical coordinates, you can use r = √(x² + y² + z²), θ = arccos(z/r), and φ = arctan(y/x).

5. What are some applications of spherical coordinates vectors?

Spherical coordinates are commonly used in physics, astronomy, and engineering, particularly for applications involving spherical or curved surfaces. Some examples of their applications include mapping the surface of the Earth, modeling planetary orbits, and calculating distances in three-dimensional space.

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