Mechanical motion-when we observe the physical objects,we find out that some of them change their position,they arein motion in reference to the other objects.. Trajectory-is sum of all positions in which a particle is found,It is linear or curved line-a)linear motion b)curvilinear motion..Mechanics is divided into two parts-kinematics and dynamics.Distance is simply the total path traversed in moving from one location or point to another.A sacalar is quantity that can be represented by a single number,numerical value-called its magnitude,along with unit of measure.

A scalar has only size ,it has no directional properities-distance ,mass. Vector is quantity that has both a size- magnitude,and the direction.We define displacement as the straight line distance between two points,along with the direction.The d is the sum of two vectors d1 and d2 and we call it the resultant of d1 and d2..In uniform motion,a particle travels the same distances in equal time intervals.s=v*t,v=s/t.In most cases the motion of a particle in nonuniform,meaning that different distances are covered in equal time intervals.Concerning the nonuniform motion,we define average sped Vp=s/t,t2-t1=tdelta,v=s2-s1/t2-t1=s delta/t delta.If the time t delta considered becomes smaller and smaller and approaches zero,the speed calculation gives an instantaneous speed