1. Introduction

1. Introduction

• In our daily life ,we see lots of things moving around for example car passing through from one place to other , person riding on a bicycle and many more like this.
• In scientific terms an object is said to be in motion ,if it changes its position with the description of time and if it does not change it position with the passage of time then it is said to be at rest
• Both the motion and rest are relative terms.
  Let us explain above statement with the help of example where mobile is kept on the table is resting at its position.
  Now what do you think about this mobile:-
  (a)is it at rest or
  (b) is it moving i.e., changing its position with the passage of time.
  Now we have stated previously that:
  

  Motion and rest are relative terms

  ☛   So for a person seeing mobile from earth it is at rest.
  ☛   Now consider a hypothetical scenario where we station our self on moon.
  ☛  Now from there earth seems to change its position with time (earth is rotating on its axis) and so mobile along with the table is changing its position.
  ☛   So, it is moving for a person tracking it from moon.
• Simplest case of motion is rectilinear motion which is the motion of the object in a straight line.
• In our description of object ,we will treat the object as an point object.
• Object under consideration can be treated as point object if the size of the object is much smaller than the distance traveled by it in a reasonable time duration for example length of a motor car traveling a distance of 500 km can be neglected w.r.t distance traveled by it.
• Here in kinematics ,we study ways to describe the motion without going into the cause of the motion.