# Velocity vector's change of direction

1. Oct 26, 2005

### boris16

hi

If an object changes it's direction but not speed, then velocity vector will only change its direction but not magnitude.

* ... delta

*r... displacement vector

Formula for velocity change is *v = *r / *time

This formula doesn't tell us anything about the direction of *v, it tells us

Same could be said for acceleration vector a. Formula will only tell you acceleration vector's magnitude, but not it's direction ( well we do know the direction is same as *v, but since we don't know the direction of *v it's of little use ) ?

bye

2. Oct 26, 2005

### Tide

The correct "formulas" are

$$\vec v = \frac {d \vec r}{dt}$$

$$\vec a = \frac {d \vec v}{dt}$$

These are vector quantities. If the direction of the velocity changes without changing the speed, the velocity and acceleration are perpendicular to each other.