text: what unit is used to measure motion?   motion itself is measured by velocity, which is defined as the change in distance over some unit of time.  in physics, the standard expression of velocity is in meters per second, or m/s.  velocity is a vector quantity, which means that it has both a magnitude (a number) and a direction (plus/minus, or compass heading, or whatever works in the context).  force, even net force, cannot be a measure of motion, because force by itself says nothing about its impact on the object -- we must also know the mass of the object to derive motion from force (force = mass*acceleration).  even then, we cannot directly compute velocity; instead, we get the acceleration of the object, which measures the change in velocity that the force brings to the object (in other words, acceleration is the change in 'meters per second,' per second, and is thus written as m/s^2).