Page 1 - Lesson Notes (Motion in a Plane)
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CLASS-XI

                                                     MOTION IN A PLANE


                                                       LESSON NOTES

               Those physical quantities which require magnitude as well as direction for their complete representation
               and follows vector laws are called vectors.

               Vectors

               1. Polar Vectors These are those vectors which have a starting point or a point of application as a
               displacement, force etc.

               2. Axial Vectors These are those vectors which represent rotational effect and act along the axis of
               rotation in accordance with right hand screw rule as angular velocity, torque, angular momentum etc


               Scalars

               Those physical quantities which require only magnitude but no direction for their complete
               representation are called scalars. Distance, speed, work, mass, density, etc are the examples of scalars.
               Scalars can be added, subtracted, multiplied or divided by simple algebraic laws.

               Different Types of Vectors

                   (i)    Equal Vectors Two vectors of equal magnitude, in same direction are called equal vectors.
                   (ii)   Negative Vectors Two vectors of equal magnitude but in opposite directions are called
                          negative vectors.
                   (iii)   Zero Vector or Null Vector A vector whose magnitude is zero is known as a zero or null
                          vector. Its direction is not defined. It is denoted by 0.
                          Velocity of a stationary object, acceleration of an object moving with uniform velocity and
                          resultant of two equal and opposite vectors are the examples of null vector.
                   (iv)   Unit Vector A vector having unit magnitude is called a unit vector. A unit vector in the

                          direction of vector A is given by  = A / A
                          A unit vector is unitless and dimensionless vector and represents direction only.

                   (v)         Orthogonal Unit Vectors The unit vectors along the direction of orthogonal axis, i.e., X – axis,
                   Y – axis and Z – axis are called orthogonal unit vectors. They are represented   I, j , k

                   (vi)     Co-initial Vectors Vectors having a common initial point, are called co-initial vectors.

                   (viii)  Coplanar Vectors Vectors acting in the same plane are called coplanar vectors.

                   (ix) Localised Vector A vector whose initial point is fixed, is called a localised vector.

                    (x) Non-localised or Free Vector A vector whose initial point is not fixed is called a nonlocalised or a
                   free vector.
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