What unit is used to measure velocity?
Velocity
metres per second
Velocity is a physical vector quantity; both magnitude and direction are needed to define it. The scalar absolute value (magnitude) of velocity is called speed, being a coherent derived unit whose quantity is measured in the SI (metric system) as metres per second (m/s) or as the SI base unit of (m⋅s−1). For example, "5 metres per second" is a scalar, whereas "5 metres per second east" is a vector. 
If there is a change in speed, direction or both, then the object has a changing velocity and is said to be undergoing an acceleration.