Friction as a force Chapter Notes | Science Class 4 ICSE PDF Download

Introduction

Friction is an important force that affects how objects move when they touch a surface. It plays a big role in our daily lives by helping us walk, hold things, and even stop vehicles. This chapter explains what friction is, how it works in different situations, its uses, its harmful effects, and ways to increase or decrease it. Through examples and activities, we learn how friction is both helpful and challenging in everyday activities.

Friction as a Force

• Friction is a force that stops or slows down the movement of an object.
• It happens when two surfaces touch or rub against each other.
• Friction acts in the opposite direction to the movement of an object.
• It helps us walk by providing grip between our feet and the ground, preventing slipping.
• Without friction, objects would keep moving forever, but too much friction can stop movement completely.
• Friction occurs in solids, liquids, and gases, but solids have more friction than liquids.
• An ice cube slides more easily than a coin on a hard surface because liquids have less friction.
• Walking on a wet floor is harder than on a dry floor due to less friction, which can cause slipping.
• The amount of friction depends on the type of surface; rough surfaces create more friction than smooth ones.
• Pushing a box on a carpet (rough surface) is harder than on a wooden floor (smooth surface) due to higher friction.

Smooth Surface vs. Rough Surface

• Heavy objects experience more friction than lighter ones, making it harder to push an iron box compared to a wooden box of the same size.
• Larger objects have more friction because they have a bigger surface area touching the ground.
• Moving a big box is harder than moving a small box of the same material due to increased friction.

Uses of Friction in Our Daily Life

• Friction gives the grip needed for stability and movement.
• It helps us hold objects like books, water bottles, and other items.
• Friction between shoe soles and the ground prevents slipping while walking.
• It allows bicycles and vehicles to move or stop due to friction between tires and the ground.
• Friction in brakes helps a car slow down or stop when brakes are applied.
• Rubbing a matchstick against a matchbox’s rough surface creates friction, which lights the matchstick.
• Rubbing hands together quickly produces heat due to friction, making hands warmer.
• Heat from lamps or electric stoves is generated because of friction.
• Friction between a violin string and its bow creates sound.
• Friction between a pencil tip and paper allows writing, while less friction on smooth butter paper makes writing difficult.
• Friction allows us to erase pencil marks with an eraser.

Harmful Effects of Friction

• Excess friction makes it hard to slide a heavy box or ride a bicycle on a rough road.
• It causes wear and tear in machine parts that rub against each other.
• Friction produces unwanted heat, wasting useful energy, and can sometimes cause fires in vehicles.
• It slows down moving objects, requiring extra force to keep them moving, which wastes fuel and energy.
• Friction in machines, like a squeaking fan, produces unwanted noise.

How to Prevent Friction?

• Friction cannot be completely removed but can be reduced using lubricants like oil, grease, or powder.
• Oiling a bicycle chain or greasing engine parts reduces friction and prevents damage.
• Oiling door hinges stops squeaking and makes them move smoothly.
• Sprinkling powder on a carrom board reduces friction, making the striker and coins move easily.
• Polishing surfaces, like slides in parks, reduces friction for smoother sliding.
• Wheels and rollers, like those on luggage bags, reduce friction, making movement easier.
• Wheels need some friction to work, as they rely on grip with the ground to move.

Increasing Friction

• Sometimes, friction needs to be increased for better grip.
• Shoe soles are grooved, and vehicle tires are treaded to increase friction with the ground.
• Increasing surface roughness helps improve grip and prevent slipping.

Terms to Know

• Friction: A force that occurs when an object moves across a surface, slowing or stopping it.
• Motion: The act of moving.
• Lubricants: Substances like oil or grease that make surfaces smoother and reduce friction.