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ATP EducationScience Exploration Notes Class 9 English Medium 2026-27
Science Exploration Notes Class 9 English Medium 2026-27 now available for students studying in cbse school, up board, state boards and international cbse schools and Latest CBSE Curriculum based on NCERT books.
Science Exploration Notes Class 9 English Medium 2026-27
All topics of Chapter 4 Describing Motion Around Us
1. Chapter Review and Key Points 2. Motion in a Straight Line 3. Measuring Motion 4. Types of Motion 5. Graphical Representation of Motion 6. Assignments - What Have You Learned?Science Exploration Chapter 4. Describing Motion Around Us
CBSE Notes New Syllabus: Class 9
Assignments - What Have You Learned?
Chapter 4. Describing Motion Around Us
This section explains the different types of motion, uniform and non-uniform motion, equations describing motion with constant acceleration, and uniform circular motion. These concepts help students understand how objects move under different conditions.
18. Types of Motion
Objects move in different ways depending on the path they follow and how their position changes with time. Based on these characteristics, motion can be classified into different types.
Classification of Motion
- Linear Motion – Motion along a straight line.
- Circular Motion – Motion along a circular path.
- Periodic Motion – Motion that repeats itself after equal intervals of time.
- Oscillatory Motion – Motion to and fro about a mean position.
Examples
- Linear Motion – Train moving on a straight track.
- Circular Motion – A stone tied to a string and rotated.
- Periodic Motion – Rotation of the Earth around the Sun.
- Oscillatory Motion – Swing moving to and fro.
19. Uniform Motion
Sometimes an object covers equal distances in equal intervals of time. Such motion is called uniform motion because the speed remains constant throughout the journey.
Definition
Uniform motion is the motion in which an object covers equal distances in equal intervals of time.
Characteristics
- Constant Speed – Speed does not change.
- Zero Acceleration – Acceleration remains zero.
- Predictable Motion – Position changes uniformly with time.
Examples
- Train – Moving with constant speed on a straight track.
- Conveyor Belt – Moving continuously at a fixed speed.
20. Non-uniform Motion
In real life, most moving objects do not travel at a constant speed. They cover unequal distances in equal intervals of time.
Definition
Non-uniform motion is the motion in which an object covers unequal distances in equal intervals of time.
Characteristics
- Changing Speed – Speed increases or decreases.
- Acceleration Present – Velocity changes with time.
- Irregular Motion – Motion is not constant.
Examples
- Car in City Traffic – Speed changes frequently.
- Cyclist on a Busy Road – Continuously speeds up and slows down.
21. Difference Between Uniform and Non-uniform Motion
| Uniform Motion | Non-uniform Motion |
|---|---|
| Equal distances in equal intervals of time. | Unequal distances in equal intervals of time. |
| Speed remains constant. | Speed changes continuously. |
| Acceleration is zero. | Acceleration is present. |
| Simple to predict. | Difficult to predict accurately. |
22. Equations of Motion (Introduction)
When an object moves with constant acceleration, its displacement, velocity, acceleration and time are related by mathematical equations called the equations of motion.
Conditions
- Motion in a Straight Line
- Constant Acceleration
Main Symbols
| Symbol | Meaning |
|---|---|
| u | Initial Velocity |
| v | Final Velocity |
| a | Acceleration |
| t | Time Taken |
| s | Displacement |
Equations
- First Equation – v = u + at
- Second Equation – s = ut + ½at²
- Third Equation – v² = u² + 2as
Applications
- Vehicle Motion – Finding speed and distance.
- Sports – Analysing the movement of athletes.
- Engineering – Designing safe transportation systems.
23. Uniform Circular Motion
An object moving along a circular path with constant speed is said to be in uniform circular motion. Although the speed remains constant, the direction changes continuously; therefore, the velocity also changes.
Definition
Uniform circular motion is the motion of an object along a circular path with constant speed.
Characteristics
- Constant Speed – Magnitude of speed remains the same.
- Changing Direction – Direction changes continuously.
- Changing Velocity – Velocity changes because direction changes.
- Acceleration Present – The object experiences centripetal acceleration towards the centre.
Examples
- Earth Revolving Around the Sun
- Moon Revolving Around the Earth
- Ceiling Fan Blades
- Hands of a Clock
- Stone Rotating on a String
24. ATP Education Concept Builder
| Concept | Key Point |
|---|---|
| Uniform Motion | Equal distances in equal time intervals. |
| Non-uniform Motion | Unequal distances in equal time intervals. |
| Uniform Circular Motion | Constant speed but changing direction. |
| Acceleration | Change in velocity per unit time. |
| Equations of Motion | Applicable only for constant acceleration. |
ATP Education Tip
Remember these important CBSE concepts: Uniform motion has constant speed and zero acceleration, whereas non-uniform motion has changing speed and non-zero acceleration. Also, in uniform circular motion the speed remains constant, but the velocity changes because the direction changes continuously. Questions based on this concept are frequently asked in competency-based and case-study sections.