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Motion
1. Motion
An object is said to be in motion when its position changes with time with respect to a fixed reference point. Example: A moving car changes its position with respect to a tree on the roadside, so it is in motion.
2. Distance
Distance is the total length of the actual path travelled by an object. Properties: It is a scalar quantity It is always positive It depends on the path followed Example: If a boy walks 4 m forward and then 3 m backward, Distance = 4 + 3 = 7 m
3. Displacement
Displacement is the shortest straight-line distance between the initial and final position of an object. Properties: It is a vector quantity It has both magnitude and direction It can be zero even when distance is not zero
Example: In the same case, Displacement = 4 − 3 = 1 m forward
4. Speed
Speed is the distance travelled per unit time. Formula: Speed = Distance / Time Unit: m/s Types of speed: Uniform speed Non-uniform speed
5. Velocity
Velocity is the displacement per unit time. Formula: Velocity = Displacement / Time Unit: m/s Velocity includes both speed and direction.
6. Uniform and Non-uniform Motion
(a) Uniform Motion
When an object covers equal distances in equal intervals of time, it is said to be in uniform motion.
(b) Non-uniform Motion
10. Graphical Representation of Motion
(a) Distance–Time Graph
For uniform motion → straight line For non-uniform motion → curved line
(b) Velocity–Time Graph
Slope of graph gives acceleration Area under the graph gives distance travelled
11. Uniform Circular Motion
When an object moves in a circular path with constant speed, it is said to be in uniform circular motion. Example: Motion of a stone tied to a string and rotated in a circle.
12. Important Points
Distance is always greater than or equal to displacement Velocity changes if either speed or direction changes Acceleration can be positive, negative, or zero Uniform circular motion involves continuous change in direction, so velocity is not constant
