Motion
Motion is change in position of an object with time . Motion of object along a straight line is called rectilinear motion . Examples include flying kite , moving train , earth ’ s rotation etc .
Frame of Reference
In order to know the change in position of an object , a reference point is required . Point O in the figure is the reference point or Origin and together with three axes , this system is called the coordinate system . A coordinate system with time frame is called frame of reference .
o
o
Objects changing positions with time with respect to the frame of reference are in motion while those which do not change position are at rest .
For a moving car , for the frame of reference outside the car , it appears moving . While for the frame of reference inside the car , the car appears stationary .