# Notation for generalized coordinates

1. Jan 14, 2016

### Isaac0427

I have seen both rk and qj both used to represent generalized coordinates in the Lagrange equations. Are these both the same things? Does it matter which you use?
Thanks!

2. Jan 14, 2016

### Orodruin

Staff Emeritus
No, what you are calling things are typically completely conventional. You could call energy R, mass x, and the speed of light T and you would have R = xT^2 - nobody would understand you if you did not specify what notation you were using though. The notation I have seen the most is to use q for generalized coordinates, but it really does not matter as long as you specify what you are doing and use a notation which is not inherently confusing.

3. Jan 14, 2016

### Isaac0427

Ok, but Wikipedia used both in the same article (even in the same equation). Are these just differing authors or is rk different?

4. Jan 14, 2016

### nasu

5. Jan 14, 2016

### Isaac0427

But they use them in replace of qj in the Lagrange equations of the first kind.

6. Jan 14, 2016

### nasu

The components of the position vectors form a possible set of "generalized" coordinates.
So you can write the equations in terms of them.
Have you read the article? The part when they say that you can go to a more general case, by defining generalized coordinates, q?