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.
- 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.