Best motion study notes for grade 9

Motion (Class 9 Physics)
Complete, detailed, notes. Every definition, term, graph, formula, and derivation is
included. These notes are exam-sufficient on their own.




1. Motion
Definition of Motion

An object is said to be in motion if its position changes with time with respect to a fixed
reference point.

Examples:

 A moving car
 Flowing water
 A flying bird

Rest

An object is said to be at rest if its position does not change with time with respect to its
surroundings.

Motion and rest are relative terms.




2. Distance and Displacement
Distance

 Total length of the actual path travelled by an object
 Scalar quantity
 SI unit: metre (m)
 Always positive

Displacement

 Shortest distance between initial and final position
 Vector quantity (has direction)
 SI unit: metre (m)
 Can be zero

Differences Between Distance and Displacement

, Distance Displacement
Scalar Vector
Actual path Shortest path
Always positive Can be zero


3. Types of Motion
(a) Rectilinear Motion

Motion along a straight line.

(b) Circular Motion

Motion along a circular path.

(c) Periodic Motion

Motion which repeats itself after equal intervals of time.

(d) Uniform Motion

An object covers equal distances in equal intervals of time.

(e) Non-Uniform Motion

An object covers unequal distances in equal intervals of time.




4. Speed
Speed

Distance travelled per unit time.

[ \text{Speed} = \frac{\text{Distance}}{\text{Time}} ]

SI Unit of Speed

 metre per second (m/s)

Types of Speed

1. Uniform Speed – constant speed
2. Non-uniform Speed – changing speed