Many physical quantities that we study can be broadly divided into two categories, known as (i) scalars and (ii) vectors.
(i) Scalars are those physical quantities which have only a magnitude. They add according to law of oridinary algebra. Mass, volume, work are some example of scalar quantities.
(ii) Vectors are physical quantities having both a magnitude and a direction. Vectors add according to triangle law of vectors and satisfy commutative property of vector addition. Velocity, acceleration, force, linear momentum are some examples of vectors.
In print; a vector represented by a bold face letter A is vector. A vector is represented by a straight line with a arrow head on it an shown in Fig is the tail and P is the head of A shown in Fig. The magnitude of vector is known as the modulous of vector. In Fig length OP, on the chosen scale; is the magnitude of A.
Two equal vectors have same magnitude and direction. The negative of a vector A, written as – A, has same magnitude as A but –A has a direction opposite to that of A as shown in Fig(b).
Vectors having equal or unequal magnitudes but acting along same or parallel lines are colinear vectors.
Vectors acting in same plane are known as coplaner vectors.
The angle θ between A and B is the angle between the two arrowed lines representing the vectors when their tails coincide as shown in Fig(a)
