— one of the main characteristics of the motion of a point. V - vector equal the limit of the ratio of growth $\vec{\Delta \mathrm{r}} $ radius vector $\vec{r}(x, y, z)$ of a point to the time interval $\Delta t$ during which growth was at decreasing unlimited $\Delta t$: $$ \vec{v}=\lim _{\Delta t \rightarrow 0} \frac{\overrightarrow{\Delta r}}{\Delta t}=\frac{\overrightarrow{d r}}{d t} $$ that $ \vec{v}$ - the first derivative of the radius vector in time. vector projection equal $$ v_{x}=\frac{d x}{d t},\ \ v_{y}=\frac{d y}{d t}, \ \ v_{z}=\frac{d z}{d t} $$ Unit V. in SI - meter per second (m/s).