# What is the difference between instantaneous velocity and speed?

##### 1 Answer

Aug 17, 2014

Velocity is a vector and speed is a magnitude.

Recall that a vector has direction and magnitude. Speed is simply the magnitude. Direction can be as simple as positive and negative. Magnitude is always positive.

In the case of positive/negative direction (1D), we can use the absolute value,

However, if the vector is 2D, 3D, or higher, you must use the Euclidean norm:

And as you can guess, 3D is: