# General Case of Relative Velocities

1. Dec 25, 2014

### Quarlep

I was looking relative velocities and I saw General case in Relativity part.That part means every direction isnt it.
http://en.wikipedia.org/wiki/Relative_velocity
and in there B is the observer or A is the observer
Thanks

2. Dec 25, 2014

### MikeLizzi

With respect to the general case of velocity addition in the wiki, there appears to be a (typo) in the formula.

I see two vectors (velocity A and velocity B) side by side in the denominator of the fraction. Most likely this is a dot product but there is no dot between them.

Yes? No?

3. Dec 25, 2014

### Staff: Mentor

$\vec{v}_{BA}$ is the velocity of B in the rest frame of A, which needs to be calculated; $\vec{v}_A$ and $\vec{v}_B$ are the velocities of A and B in some other frame, which are presumed to be known at the start of the calculation.

Yes, there should be a dot between them.