Physics XI Content
UNIT VECTORFREE VECTORPOSITION VECTORNULL VECTOR


UNIT VECTOR


“A unit vector is defined as a vector in any specified direction whose magnitude is unity i.e. 1. A unit vector only specifies the direction of a given vector. “ 

A unit vector is denoted by any small letter with a symbol of arrow hat ().  
A unit vector can be determined by dividing the vector by its magnitude.  
For example unit vector of a vector A is given by:  
In threedimensional coordinate system unit vectors having the direction of the positive Xaxis, Yaxi and Zaxis are used as unit vectors. These unit vectors are mutually perpendicular to each other.  
FREE VECTOR


A vector that can be displaced parallel to itself and applied at any point is known as a FREE VECTOR.  
A free vector can be specified by giving its magnitude and any two of the angles between the vector and coordinate axes.  
POSITION VECTOR


A vector that indicates the position of a point in a coordinate system is referred to as POSITION VECTOR.  
Suppose we have a fixed reference point O, then we can specify the position of a given point P with respect to point O by means of a vector having magnitude and direction represented by a directed line segment OP. This vector is called POSITION VECTOR.  
In a threedimensional coordinate system if O is at origin then, O(0,0,0) and P is any point say P(x, y,z)  
in this situation position vector of point P will be:  
NULL VECTOR


A null vector is a vector having magnitude equal to zero. It is represented by. A null vector has no direction or it may have any direction. Generally a null vector is either equal to resultant of two equal vectors acting in opposite directions or multiple vectors in different directions.  