Find a normal vector to a unit sphere using cartesian coordinates

In summary, the conversation discusses finding the unit normal vector on the surface of a unit sphere centered at the origin, using Cartesian unit vectors and equations involving dot and cross products. It is suggested that any nonzero vector could be a normal at some point on the surface, and the use of the gradient of a function is also mentioned.
  • #1
Frozen Light
14
0

Homework Statement


Consider a unit sphere centered at the origin. In terms of the Cartesian unit vectors i, j and k, find the unit normal vector on the surface

Homework Equations


A dot B = AB cos(theta)
A cross B = AB (normal vector) sin(theta)
Unit sphere radius = 1

The Attempt at a Solution


Isn't any direction a normal vector?
i x j = + k
j x i = - k
etc.
 
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  • #2
Frozen Light said:

Homework Statement


Consider a unit sphere centered at the origin. In terms of the Cartesian unit vectors i, j and k, find the unit normal vector on the surface

Homework Equations


A dot B = AB cos(theta)
A cross B = AB (normal vector) sin(theta)
Unit sphere radius = 1

The Attempt at a Solution


Isn't any direction a normal vector?
i x j = + k
j x i = - k
etc.
Any nonzero vector would be a normal at some point on the surface of the sphere. My guess is that you should take an arbitrary point P(x, y, z) on the surface, and find the normal to it. If that's what is wanted in the problem, it could have been written more clearly.
 
  • #3
Thank you, that would make a bit more sense.
 
  • #4
The unit sphere is of the form [itex]x^2+ y^2+ z^2= 1[/itex]. You can think of that as a 'Level Surface" of the function [itex]F(x, y, z)= x^2+ y^2+ z^2[/itex] and use the fact that the gradient of such a function, [itex]\nabla F[/itex], is always normal to level surfaces.
 
  • #5
Or think about what direction a position vector to a point on the sphere has.
 

Related to Find a normal vector to a unit sphere using cartesian coordinates

1. How do you find a normal vector to a unit sphere using cartesian coordinates?

To find a normal vector to a unit sphere using cartesian coordinates, you can use the equation n = (x, y, z) where x, y, and z are the coordinates of a point on the sphere's surface. This will give you a vector that is perpendicular to the surface of the sphere at that point.

2. What is the formula for a unit sphere in cartesian coordinates?

The formula for a unit sphere in cartesian coordinates is x^2 + y^2 + z^2 = 1. This means that for any point on the sphere's surface, the sum of the squares of its x, y, and z coordinates will equal 1.

3. Can you explain the concept of a normal vector in relation to a unit sphere?

A normal vector is a vector that is perpendicular to a surface at a given point. In the case of a unit sphere, the normal vector at any point on its surface will be a vector that points directly away from the center of the sphere and has a length of 1.

4. How does finding a normal vector to a unit sphere relate to surface normal vectors?

Surface normal vectors are used to describe the orientation of a surface at a given point. In the case of a unit sphere, the normal vector at any point on its surface can be used as a surface normal vector to describe the orientation of the sphere's surface at that point.

5. Can a normal vector to a unit sphere be found using other coordinate systems?

Yes, a normal vector to a unit sphere can also be found using spherical coordinates or cylindrical coordinates. However, the cartesian coordinate system is the most commonly used method for finding a normal vector to a unit sphere.

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