# About momentum operator in other coordinate system

1. Dec 19, 2008

### KFC

Hi there, does anyone know where can I found a material or note about how to deduce momentum operator in coordinate system other than linear coordinate (especially in spherical coordinate system)?

2. Dec 20, 2008

### George Jones

Staff Emeritus
Express the other coordinates in terms of $x$, and $y$, and $z$, and then use the chain rule. For example,

$$\frac{\partial}{\partial x} = \frac{\partial r}{\partial x}\frac{\partial}{\partial r} + \frac{\partial \phi}{\partial x}\frac{\partial}{\partial \phi} + \frac{\partial \theta}{\partial x}\frac{\partial}{\partial \theta}.$$