🔬 Class 8 Science – Exploring Forces Original Visual Revision Notes
Based on NCERT “Curiosity” 2024 textbook. For personal study only. Simple words used for different learners. Not a replacement for the official textbook.
🌐 Real-World Connection: When you kick a football, push a door open, pull a drawer out, or stop a rolling ball with your foot — you are using force! Force is the push or pull that makes things move, stop, speed up, slow down, or change direction. Even sitting on a chair uses force — your weight pushes down and the chair pushes back. Everything that moves in this world does so because of forces, and this chapter explains them all.
💪 Topic 1: What is Force?
Force is a push or a pull.
Force makes things move or stop.
We cannot see a force itself.
Force has size and a direction.
Force needs two things to work.
🖐 Topic 2: Push and Pull
Push moves things away from you.
Pull brings things closer to you.
Kicking a ball is a push force.
Pulling a rope is a pull force.
Both push and pull are forces.
✋ Topic 3: Contact Forces
Contact force needs touching the thing.
Friction slows things that rub together.
Muscular force comes from our body.
Spring force comes from a stretched spring.
You push a door with contact force.
🪜 Topic 4: Non-Contact Forces
No touching is needed for these forces.
Gravity pulls everything down to Earth.
Magnetic force pulls iron things closer.
Electrostatic force comes from rubbed things.
A magnet picks up pins without touch.
🌟 Topic 5: Effects of Force
Force can make things move faster.
Force can make things move slower.
Force can change the direction of things.
Force can change the shape of things.
A ball changes shape when you squeeze.
🔥 Topic 6: Friction
Friction happens when two things rub together.
Rough things have more friction on them.
Smooth things have less friction on them.
Friction makes heat when things rub fast.
Friction helps us walk without falling down.
🔧 Topic 7: Increase and Decrease Friction
Rough surfaces make more friction on things.
Smooth surfaces make less friction on things.
Oil and grease reduce friction a lot.
Treads on tyres increase friction for grip.
Powder on hands helps us grip things.
🌊 Topic 8: Fluid Friction
Water and air are called fluids here.
Fluids also slow down moving things a lot.
This slowing is called fluid friction or drag.
Streamlined shapes cut through fluids well.
Fish and birds have streamlined body shapes.
🌎 Topic 9: Force of Gravity
Earth pulls all things towards its centre.
This pull is called the force of gravity.
Things fall down because of gravity always.
Moon also has gravity but it is less.
Gravity keeps us on the ground safely.
⚖️ Topic 10: Weight vs Mass
Mass is how much matter is inside.
Weight is gravity pulling on that mass.
Mass stays the same on Moon or Earth.
Weight changes if gravity is different there.
Weight is measured in newtons, mass in kg.
🎨 Section 2 – Visual Diagrams
Fig 1 – Push moves things away. Pull brings things closer.
Fig 2 – Contact forces need touch. Non-contact forces work from far.
Fig 3 – Force can change speed, direction, or shape of things.
Fig 4 – Rough surfaces make more friction. Smooth surfaces make less.
Fig 5 – Fish and birds have shapes that reduce fluid friction.
✏️ Section 3 – Worked Examples
💡 Example 1: Finding the type of force
Question: A magnet picks up a pin. What force is this?
1
Think: Does the magnet touch the pin? No.
2
No touch means it is a non-contact force.
3
A magnet uses magnetic force to pull iron.
✔ Answer: This is magnetic force. It is non-contact.
💡 Example 2: Effect of force on shape
Question: You press a rubber ball. What happens?
1
Your hand puts force on the ball.
2
The ball gets squeezed and changes shape.
3
This shows force can change shape of things.
✔ Answer: Force changes the shape of the ball.
💡 Example 3: Weight on Moon vs Earth
Question: A boy has mass 30 kg. His weight on Earth is 300 N. What about on Moon?
1
Mass stays the same everywhere: 30 kg.
2
Moon has less gravity than Earth has.
3
Moon gravity is about one-sixth of Earth gravity.
4
Weight on Moon = 300 ÷ 6 = 50 N.
✔ Answer: Mass is 30 kg (same). Weight on Moon is 50 N (less).
🔢 Section 4 – Quick Reference Table
#
Idea
What It Means (Simple Words)
Example
1
Force
A push or a pull on something.
Pushing a door open.
2
Contact Force
Force that needs touching the thing.
Kicking a football.
3
Non-Contact Force
Force that works without any touching.
Magnet pulling a nail.
4
Friction
Force that slows rubbing things down.
Brakes stop a bicycle.
5
Muscular Force
Force from muscles in our body.
Lifting a heavy bag.
6
Spring Force
Force from a stretched or pressed spring.
A spring toy jumps up.
7
Gravity
Earth pulls all things down to it.
An apple falls from tree.
8
Magnetic Force
Force from a magnet on iron things.
Magnet sticks to fridge.
9
Electrostatic Force
Force from rubbed things on light objects.
Rubbed comb picks up paper.
10
Streamlined Shape
Narrow smooth shape that cuts through fluid.
Shape of a fish body.
11
Mass
How much matter is in a thing.
Measured in kilograms (kg).
12
Weight
How hard gravity pulls on a thing.
Measured in newtons (N).
📝 Section 5 – Hands-On Practice
Part A: Name the Force
Write the type of force for each action below:
1. A boy lifts a box. → ___________
2. A magnet pulls a paper clip. → ___________
3. A ball rolls and stops slowly. → ___________
4. An apple falls from a tree. → ___________
5. Rubbed balloon sticks to wall. → ___________
Part B: Contact or Non-Contact?
Write C for Contact or N for Non-Contact:
1. Pushing a door ___
2. Gravity pulling a ball ___
3. Rubbing hands together ___
4. Magnet attracting iron ___
5. Kicking a stone ___
Part C: True or False?
1. Friction always helps us. ___
2. Oil reduces friction between surfaces. ___
3. Mass changes when you go to Moon. ___
4. Weight is measured in kilograms. ___
5. Streamlined shapes reduce fluid friction. ___
Part D: Fill in the Blanks
1. Force is a _______ or a _______.
2. _______ force needs touching the thing.
3. Earth pulls things down with _______ force.
4. Friction can be reduced by using _______.
5. Fish have _______ shapes to swim easily.
Part E: Draw and Label
Draw a picture of each one below:
1. A person pushing a box (show force arrow).
2. A magnet pulling a nail (show force arrow).
3. A streamlined fish shape in water.
✅ Detailed Solutions — Section 5
Part A: Name the Force
A boy lifts a box → Muscular force
A magnet pulls a paper clip → Magnetic force
A ball rolls and stops slowly → Friction
An apple falls from a tree → Gravitational force
Rubbed balloon sticks to wall → Electrostatic force
Part B: Contact or Non-Contact?
Pushing a door → C (Contact — you touch the door)
Gravity pulling a ball → N (Non-Contact — Earth pulls without touching)
Rubbing hands together → C (Contact — hands touch each other)
Magnet attracting iron → N (Non-Contact — works at a distance)
Kicking a stone → C (Contact — foot touches the stone)
Part C: True or False?
False — Friction does not always help. In engines and machines it wastes energy and causes wear; it hinders as well as helps.
True — Oil fills the tiny gaps between surfaces, reducing direct contact and lowering friction.
False — Mass is the amount of matter in an object and stays the same everywhere, including the Moon.
False — Weight is measured in newtons (N), not kilograms. Kilograms measure mass.
Friction can be reduced by using oil / lubricants / smooth surfaces.
Fish have streamlined shapes to swim easily.
Part E: Draw and Label
Person pushing a box: Draw a stick person with hands on a box. Draw a bold arrow pointing in the direction of push. Label the arrow "Force (Push)".
Magnet pulling a nail: Draw a U-shaped magnet near an iron nail. Draw an arrow from the nail pointing toward the magnet. Label "Magnetic Force (non-contact)".
Streamlined fish: Draw a smooth oval body tapering to a pointed nose at the front and a tail fin at the back. Draw curved arrows flowing smoothly around the body. Label "Streamlined shape reduces drag".
🃏 Section 6 – Flip & Learn Cards
👈 Click each card to see the answer!
🔬 What is force?
Force is a push or a pull on something.
✋ What is contact force?
A force that needs touching the object.
🪜 What is non-contact force?
A force that works without any touch.
🔥 What does friction do?
Friction slows things that rub together.
🌎 What is gravity?
Earth pulls all things down to its centre.
⚖️ How are mass and weight different?
Mass is how much matter. Weight is gravity pulling on it.
🐟 What is a streamlined shape?
A smooth narrow shape. It cuts through fluids easily.
🔧 How can we reduce friction?
Use oil, grease, or make surfaces smooth.
🧠 Section 7 – Mind Map
Mind Map – All the big ideas of Forces in one picture.