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4 Common types of friction you need to know

4 Common types of friction you need to know

In our fast-paced world, we tend to miss out on the everyday things that really shape how we live.

While often seen as a roadblock, friction is easily one of our most important and invisible allies. In fact, it's the basic rule that affects the way we move, work, and play.

From activities such as walking down the street to unwanted forest fires (trees rubbing against one another), friction has its fingerprints all over planet earth!

In this article, we’ll be taking a closer look at how the different types of friction affect our daily lives.

What’s friction

Friction is a force that opposes the relative motion or tendency of motion between two surfaces in contact. Think of it as the 'stickiness' between things when they rub against each other. 

Let’s say you’re trying to slide a book to a friend seated across the table. The table's surface and the book's cover have tiny bumps and rough spots that catch onto each other. These little bumps then create a force known as friction that makes it harder to slide the book smoothly.

And if you push the book faster across the table, you'll experience a stronger resistance due to the rough surfaces interacting more intensely. Similar to trying to run through tall grass, the grass pushes back and makes movement tougher as you pick up speed.

The increased interaction also creates heat, warming up the book or table because friction converts some of your pushing energy (kinetic energy) into heat energy. On top of that, the heightened friction can lead to additional wear and tear on both the book's cover and the table's surface over time, as the rubbing and bumping wear away tiny bits, similar to how shoes' soles or car tires wear out from prolonged friction.

Effects of friction on our daily life

Friction has numerous effects on our daily lives, influencing various activities and objects. 

Some examples:

Walking and Running: Friction between our shoes and the ground provides the grip needed to walk and run without slipping.

Braking in Vehicles: Friction between brake pads and a vehicle's wheels enables effective braking, allowing us to slow down and stop safely.

Writing with Pencils or Pens: Friction between the pencil or pen tip and the paper's surface allows us to create marks while writing.

Gripping Objects: Friction between our hands and objects like utensils, tools, or doorknobs enables us to hold and manipulate them.

Rubbing Hands Together for Warmth: The friction generated when rubbing our hands together produces heat, helping us warm up in cold weather.

Using Braille: Friction enables individuals who are visually impaired to read Braille text by feeling the raised dots.

Playing Musical Instruments: Musicians rely on friction between their fingers and instrument surfaces to create sounds while playing strings, keys, or other components.

Types of friction

#1 Static friction

Static friction refers to the force that prevents an object from starting its motion when a force is applied to it. It's the friction that exists when two surfaces are in contact but not moving relative to each other.

Examples of static friction:

Pushing a stuck car
Imagine you're trying to push a car that's stuck in mud or on an incline. Initially, it doesn't budge despite your efforts. The force you apply is countered by the static friction between the car's tires and the ground. Once the force you apply overcomes this static friction, the car starts moving.

Opening a Jar Lid
Let’s say you’re trying to open the lid of the pickle jar. As you twist the lid, there's an initial resistance before it starts to turn. This resistance is due to the static friction between the lid and the jar's rim. You need to apply enough force to overcome the static friction, and once the lid starts moving, it becomes easier to continue twisting it.

#2 Sliding friction

Sliding friction, also known as kinetic friction, refers to the force that opposes the motion of two surfaces sliding past each other. It comes into play when there’s relative motion between the surfaces in contact.

Examples of sliding friction:

Sliding Down a Slide
As you slide down, the contact between your clothing and the slide's surface creates sliding friction. This friction slows down your descent, allowing you to reach a controlled and safe speed.

Braking a Bicycle
When you apply the brakes on a bicycle, the brake pads press against the wheel rims. This contact generates sliding friction that slows down the rotation of the wheels. The friction converts the kinetic energy of the moving bicycle into heat energy, which is why you might feel the rims getting warmer after braking.

#3 Rolling friction

Rolling friction is the force that resists the motion of a round object (like a wheel or a ball) as it rolls on a surface. It's different from sliding friction because it pertains to objects that rotate or roll while moving.

Examples of rolling friction:

When you glide on roller skates, the wheels roll on the ground. Rolling friction between the wheels and the skating surface allows you to move with less resistance compared to sliding friction, making roller skating a smoother experience.

Pulling luggage
Rolling suitcases or luggage equipped with wheels use rolling friction to glide smoothly through airports or train stations. This type of friction makes it much more convenient to transport heavy bags without lifting them off the ground.

#4 Fluid Friction

Fluid friction is a kind of resistance that happens when things move through liquids (like water) or gases (like air). It's what makes it a bit harder to move in these substances.

Examples of fluid friction:

When you swim through water, your body encounters fluid friction. The water's resistance to your motion creates drag, making it harder to move quickly. Swimmers often adjust their techniques or swim gear to minimise fluid friction and glide more smoothly through the water.

While riding a bicycle, you experience fluid friction in the form of air resistance. As you move through the air, the air molecules create resistance that opposes your forward motion. This is why cyclists often crouch low on their bikes to reduce the effects of air resistance and increase their speed.

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