Q.What is meant by position vector of a point?

The position vector of a point is the vector from the origin of the coordinate system to that point; it fixes the point's location completely (distance and direction).

To describe the location of a particle in space we first choose a convenient origin O and a set of coordinate axes. The position vector $\vec{r}$ of a point P is then defined as the vector drawn from the origin O to the point P.

In a plane (2-D), if P has coordinates (x, y), the position vector is

$\vec{r} = x\hat{i} + y\hat{j}$

where $\hat{i}$ and $\hat{j}$ are the unit vectors along the x and y axes.

In three dimensions, $\vec{r} = x\hat{i} + y\hat{j} + z\hat{k}$.

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