# Homework Help: Quick vector notation question

1. Feb 24, 2010

### jumbogala

1. The problem statement, all variables and given/known data
My prof has written out a derivation which says:

$$\vec{a_{t}}$$ = α x $$\vec{r}$$

Why does everything except α have a vector sign on it? I think α should be a vector here too...

By the way, he also derived dv/dt = ω, and v had a vector symbol but ω did not. Is that right or should ω be a vector?

2. Relevant equations

3. The attempt at a solution

2. Feb 24, 2010

### tiny-tim

Hi jumbogala!

You're right, he's wrong!

(there's probably some psychological reason for it! )

Yes, α and ω are definitely vectors, exactly like a and r.