Motion in straight line
Position :
(i) Position is a place where someone or something is located or has been put. In physics, position is usually a number on an axis.
Rest and Motion:
(i) Rest: An object is said to be at rest if it does not change its position w.r.t. its surroundings either passage of time. For example, a book placed on the table remains on the table i.e. it does not change its position with time w.r.t. its surroundings. We say that the book is at rest.
(ii) Motion: An object is said to be in motion if it changes its position w.r.t. its surroundings with the passage of time. For example, a speeding car is in motion because as the time passes, the car changes its position w.r.t. its surroundings e.g. electric poles, trees, buildings etc.
Rest and motion are relative. They are not absolute.
Example:
The driver of a moving bus is at rest with respect to a person sitting inside the bus and is in motion with respect to a standing person outside the bus. Therefore rest and motion are relative.
Path length (Distance) :
(i) The total length of the path is known as distance.
(ii) Distance is a Scalar
Displacement:
(i) The shortest distance between two points with specific direction is known as displacement.
(ii) Displacement is a vector.
(iii) Both distance and displacement have same units and dimensions.
(iv) Unit of displacement is m
(v) Dimensional formula of displacement is
Examples:
