- #1
medwatt
- 123
- 0
Hello,
In Cartesian coordinates, if we have a point P(x1,y1,z1) and another point Q(x,y,z) we can easily find the displacement vector by just subtracting components (unit vectors are not changing directions) and dotting with the unit products. In fact we can relate any point with a position vector by drawing a vector from the origin to the point.
Now when it comes to cylindrical coordinates for some reason the two books I have don't seem to take this approach to find the position vectors of any two points P(r1,θ1,z1) and Q(r,θ,z). What they seem to do is go through Cartesian coordinates, i.e. write each point with its equivalent Cartesian coordinates representation and using a transformation matrix we get the displacement vector in cylindrical coordinates.
So given that a vector in space doesn't know (or care) about the coordinate system used a point P which is given by (x,y,z) in Cartesian coordinates can be transformed to cylindrical coordinates (r,θ,z) using x=r*cos(θ), y=r*sin(θ), z=z. So a position vector in Cartesian is <x,y,z>.
The questions:
1. I want to know how to represent any vector in cylindrical coordinates (eg. A=2[itex]\hat{r}[/itex]+3[itex]\hat{θ}[/itex]+5[itex]\hat{z}[/itex].) I'm asking this because a point P(2,3,5) in the cylindrical system does not correspond to a vector A=2[itex]\hat{r}[/itex]+3[itex]\hat{θ}[/itex]+5[itex]\hat{z}[/itex].
2. I want to ignore Cartesian coordinates and use just the pure geomtry of the cylindrical system to write the displacement vector.
Any explanation or material is welcomed.
In Cartesian coordinates, if we have a point P(x1,y1,z1) and another point Q(x,y,z) we can easily find the displacement vector by just subtracting components (unit vectors are not changing directions) and dotting with the unit products. In fact we can relate any point with a position vector by drawing a vector from the origin to the point.
Now when it comes to cylindrical coordinates for some reason the two books I have don't seem to take this approach to find the position vectors of any two points P(r1,θ1,z1) and Q(r,θ,z). What they seem to do is go through Cartesian coordinates, i.e. write each point with its equivalent Cartesian coordinates representation and using a transformation matrix we get the displacement vector in cylindrical coordinates.
So given that a vector in space doesn't know (or care) about the coordinate system used a point P which is given by (x,y,z) in Cartesian coordinates can be transformed to cylindrical coordinates (r,θ,z) using x=r*cos(θ), y=r*sin(θ), z=z. So a position vector in Cartesian is <x,y,z>.
The questions:
1. I want to know how to represent any vector in cylindrical coordinates (eg. A=2[itex]\hat{r}[/itex]+3[itex]\hat{θ}[/itex]+5[itex]\hat{z}[/itex].) I'm asking this because a point P(2,3,5) in the cylindrical system does not correspond to a vector A=2[itex]\hat{r}[/itex]+3[itex]\hat{θ}[/itex]+5[itex]\hat{z}[/itex].
2. I want to ignore Cartesian coordinates and use just the pure geomtry of the cylindrical system to write the displacement vector.
Any explanation or material is welcomed.