Velocity (metric system) as metres per second (m/s) or as the SI base unit of (m⋅s). 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". To have a constant velocity, an object must have a constant speed in a constant direction. Constant direction constrains the object to motion in a straight path thus, a constant velocity means motion in a straight line at a constant speed. For
Angular velocity a true vector, rather than just a pseudo-vector. The only non-obvious property of the above addition is commutativity. This can be proven from the fact that the velocity tensor "W" (see below) is skew-symmetric, so that formula_34 is a rotation matrix which can be expanded as formula_35. The composition of rotations is not commutative, but formula_36 is commutative to first order, and therefore formula_37. Notice that this also defines the substraction as the addition of a negative vector. Given a rotating frame of three unit coordinate vectors, all the three must have the same angular speed at each instant. In