Table of Contents
- Rest
- Motion
- Rest and Motion are Relative Terms
- Absolute rest and motion
- Important Point Regarding Absolute Rest and Motion
Rest
An object is said to be at rest if it does not change its position w.r.t. its surroundings with the passage of time e.g., a book lying on a table.
Motion
An object is said to be in motion if it changes its position w.r.t. its surroundings with the passage of time e.g., a train moving on rails.
Rest and Motion are Relative Terms
Rest and motion are relative terms. A passenger sitting in a moving train is at rest with respect to his fellow passengers, but he is in motion with respect to the objects outside the train. Thus, an object may be at rest w.r.t. one object and at the same time it may be in motion relative to another object. Hence rest and motion are relative terms.
Absolute rest and motion
In order to know whether the position of an object changes with time or not, a point absolutely fixed in space has to be chosen as reference point. But no such point is known in the universe. The earth revolves around the sun, the entire solar system travels through our own galaxy, the milkyway and clusters of galaxies move with respect to other clusters. So no object in the universe is in a state of absolute rest.
Important Point Regarding Absolute Rest and Motion
As no object in the universe is at absolute rest, so the absolute motion cannot be realised. Only relative rest and relative motion can be realised.