**Scalar and vector quantities:** The physical quantities which have only magnitude and need no idea of direction are called scalar quantities.

**For example:** Speed, mass, time, length, area, volume, density, work, energy etc.

**Vector quantities:** There are certain quantities which require magnitude as well as direction, to express them clearly, i.e., the physical quantities which have magnitude, as well as direction, are called vector quantities.

**For example:** Velocity, acceleration, force, pressure etc.

**Vector representation:** A vector quantity is represented by a single arrow. It is written as \(\bar { AB } \). Here, length of AB is the magnitude of |\(\bar { AB } \)|.

**Unit Vector**

A unit vector is a vector whose magnitude is unit and direction is the direction of the vector, say \(\bar { AB } \). A unit vector is denoted by \(\hat { A } \) and it is read as A cap.

\(\bar{A} =|\bar{A}|\hat {A} =\hat{A} =\frac{\bar{A}}{|\bar{A}|} \)