# Cartesian to Cylindrical coordinates?

## Homework Statement

I want to convert R = xi + yj + zk in to cylindrical coordinates and get the acceleration in cylindrical coordinates.

z

## The Attempt at a Solution

I input the equations listed into R giving me:

R =
i +
j + z k

Apply chain rule twice:

How do I get this final answer? It looks like the terms with sin were dropped. How does this happen?

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Orodruin
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Homework Helper
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Your result is an expression for the acceleration using the Cartesian vector basis (i.e., you are showing the Cartesian components expressed in terms of the cylinder coordinates). You need to relate this to the vector components using the cylinder coordinate basis vectors.

Your result is an expression for the acceleration using the Cartesian vector basis (i.e., you are showing the Cartesian components expressed in terms of the cylinder coordinates). You need to relate this to the vector components using the cylinder coordinate basis vectors.
I don't think I understand. By basis you mean the unit vectors in rHat, thetaHat, zHat?

Orodruin
Staff Emeritus
Homework Helper
Gold Member
Yes, that is the basis that you should be using to express your vector as done in the quoted result.

Yes, that is the basis that you should be using to express your vector as done in the quoted result.
So I have:

I don't see how I replace i,j,k with these to get the answer.

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Orodruin
Staff Emeritus
Homework Helper
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You have a result for your vector. You need to express it as a linear combination of the vector basis, i.e., you need to find ##v_r##, ##v_\theta## and ##v_z## such that
$$\vec v = v_r \hat r + v_\theta \hat \theta + v_z \hat z.$$
Since you have three components, this is a system of three equations for three unknowns.

You have a result for your vector. You need to express it as a linear combination of the vector basis, i.e., you need to find ##v_r##, ##v_\theta## and ##v_z## such that
$$\vec v = v_r \hat r + v_\theta \hat \theta + v_z \hat z.$$
Since you have three components, this is a system of three equations for three unknowns.

I see it. Thanks!