تكملة 3 A scalar is any positive or negative physical quantity that can be
completely specified by its magnitude.
A vector is any physical quantity that requires both a magnitude and
direction for its complete description. A vector is shown graphically by
an arrow. The length of the arrow represents the magnitude of the
vector, and a fixed axis defines the direction of its line of action .The
head of the arrow indicates the sense of direction of the vector (Fig 2-1)

Fig(a)
2.2 Vector operations:-

Multiplication and division of vector by a scalar:
If a vector is multiplied by a positive scalar, its magnitude is increased
by that amount. When multiplied by a negative scalar it will also
change the directional sense of the vector (Fig 2-2).

Amrani
Vector addition
All vector quantities obey the parallelogram law of addition. Fig 2-3 and Fig 2-4 and Fig 2-5 illustrates addition of vectors ?? and ?? to obtain a resultant ?? .