NCERT Class 9 Science Exploration: Chapter 6 — 6. How Forces Affect Motion
This chapter, '6. How Forces Affect Motion,' from NCERT's Class 9 Science Exploration textbook, delves into the fundamental concept of force and its effects on objects. It revisits the understanding that a force can initiate motion, alter speed and direction, or change an object's shape. The chapter emphasizes that force is a vector quantity, requiring both magnitude and direction for its description, similar to position, velocity, and acceleration. It introduces the SI unit of force as the newton (N) and explains how a spring balance can measure force magnitude. The text also begins to explore balanced and unbalanced forces, noting that multiple forces often act simultaneously on an object in real-life scenarios. This foundational understanding of force is crucial for comprehending the causes of motion and subsequent topics in physics.
Quick info
| Board | CBSE / NCERT |
|---|---|
| Class | Class 9 |
| Subject | Science |
| Book | Exploration |
| Chapter | Chapter 6 — 6. How Forces Affect Motion |
| Language | English |
| PDF type | NCERT Textbook |
| Session | CBSE 2026 |
| Reading time | 4 minutes |
| Word count | 658 |
Learning outcomes
- Define force and its effects on objects.
- Understand that force is a vector quantity with magnitude and direction.
- Identify the SI unit of force as the newton (N).
- Recognize how a spring balance measures force.
- Differentiate between situations with single and multiple forces acting on an object.
Vocabulary
| Word | Meaning |
|---|---|
| 6. How Forces Affect Motion | A push or pull that can change the motion, speed, direction, or shape of an object. |
| Newton | The SI unit of force, symbolized by N. |
| Magnitude | The size or strength of a force. |
| Direction | The line along which something moves or is aimed. |
| Spring balance | A device used to measure the magnitude of a force, including weight. |
| Friction | A force that opposes motion between surfaces in contact. |
| Gravitational force | The force of attraction between any two objects with mass. |
| Buoyant force | An upward force exerted by a fluid that opposes the weight of an immersed object. |
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Practice questions
- What are the effects of a force on an object? Answer: A force can make an object move from rest, change its speed or direction, or change its shape.
- What is the SI unit of force? Answer: The SI unit of force is the newton (N).
- Why is direction important when describing a force? Answer: Direction is important because force is a vector quantity, and its effect depends on the direction in which it is applied.
- Name a device used to measure the magnitude of a force. Answer: A spring balance can be used to measure the magnitude of a force.
Frequently asked questions
What is a force?
A force is a push or pull that can cause an object to start moving, stop moving, change its speed or direction, or change its shape.
What are the effects of applying a force?
A force can make a stationary object move, change the speed or direction of a moving object, or deform an object.
What is the SI unit of force?
The SI unit of force is the newton, symbolized as N.
How is force measured?
The magnitude of a force can be measured using a spring balance.
Why is direction important for a force?
6. How Forces Affect Motion is a vector quantity, meaning it has both magnitude and direction. The effect of a force depends on both.
Do forces always act alone?
No, in real-life situations, multiple forces usually act on an object simultaneously.
Related resources
Important topics
Topics covered
NCERT Class 9 Science — Exploration — Chapter 6 — 6. How Forces Affect Motion. Verified by NCERT Help Editorial Team. Reviewed on 29 Jul 2026. Last updated 10 Aug 2026.