FrictionFriction

D. Crowley, 2007D. Crowley, 2007

FrictionFriction

To understand what friction is, and how this affects movement

To understand what friction is, and how this affects movement

Wednesday, April 19, 2023Wednesday, April 19, 2023

What is friction?What is friction? Rub your hands together quickly - what do you notice?

This is first hand experience of friction!

Rub your hands together quickly - what do you notice?

This is first hand experience of friction!

Riding your bikeRiding your bike

Before we define what friction is, think about riding your bike

What do you think affects how quickly your bike can stop? See if you and a partner can come of with three factors affecting a bike’s stopping potential

Before we define what friction is, think about riding your bike

What do you think affects how quickly your bike can stop? See if you and a partner can come of with three factors affecting a bike’s stopping potential

Stopping the bikeStopping the bike Type of surface you are cycling on - road /

gravel / ice / mud?! How quickly you are going - the faster you go, the

longer it takes to stop

Type of brakes you have - the better the brakes (e.g. disc brakes) the quicker they can stop you

How good are your tyres? Do they grip the road well, or are they more like slicks?

How much are you carrying - the more you have on your bike the more energy you will have at a given speed - so the more energy it will take to stop you!

Type of surface you are cycling on - road / gravel / ice / mud?!

How quickly you are going - the faster you go, the longer it takes to stop

Type of brakes you have - the better the brakes (e.g. disc brakes) the quicker they can stop you

How good are your tyres? Do they grip the road well, or are they more like slicks?

How much are you carrying - the more you have on your bike the more energy you will have at a given speed - so the more energy it will take to stop you!

FrictionFriction

Friction is a force which occurs when two objects interact

If an object has no force propelling it, it will slow down and eventually stop due to friction

Rubbing your hands together causes friction - causing your hands to heat up

Friction can occur in many ways, including the following…

Friction is a force which occurs when two objects interact

If an object has no force propelling it, it will slow down and eventually stop due to friction

Rubbing your hands together causes friction - causing your hands to heat up

Friction can occur in many ways, including the following…

FrictionFriction Friction occurs between solid surfaces which are gripping /

sliding past each other (e.g. a tyre on the road / marble down a ramp)

Resistance (drag) from the air or liquid - as you move air or liquid particles collide into you (this is why a parachute slows you down and to go very fast cars need to become streamlined)

Friction increases as speed increases - more speed = more air particles colliding into you

Friction occurs between solid surfaces which are gripping / sliding past each other (e.g. a tyre on the road / marble down a ramp)

Resistance (drag) from the air or liquid - as you move air or liquid particles collide into you (this is why a parachute slows you down and to go very fast cars need to become streamlined)

Friction increases as speed increases - more speed = more air particles colliding into you

Friction between two surfaces Friction increases as speed does Air resistance - example of friction

EnquiryEnquiry

Your task is to investigate how quickly you can get a block of wood to slide down a drain pipe

You have a variety of materials to help you achieve this, including: foil; dusters; polish; doweling etc...

You must think about what results you want to collect, and what bits of information you must record

What must you keep the same during the experiment and why? How can you measure the objects speed - what information do you need to collect to calculate this?

Your task is to investigate how quickly you can get a block of wood to slide down a drain pipe

You have a variety of materials to help you achieve this, including: foil; dusters; polish; doweling etc...

You must think about what results you want to collect, and what bits of information you must record

What must you keep the same during the experiment and why? How can you measure the objects speed - what information do you need to collect to calculate this?

EnquiryEnquiry

You need to write down on the sheet a short draft of the experiment your are going to do + a hypothesis of what you think will happen

What variables are you changing / keeping the same?

How are you going to measure the results (what will be in your table, and will you repeat)?

Conclusion - what do you find out?

You need to write down on the sheet a short draft of the experiment your are going to do + a hypothesis of what you think will happen

What variables are you changing / keeping the same?

How are you going to measure the results (what will be in your table, and will you repeat)?

Conclusion - what do you find out?

Some surfaces limited the speed the block moved at, due to much greater frictional forces

All bad?All bad? Friction, such as air resistance slows objects down

But it is not always bad - you and your partner now need to write down some examples of friction when it is being bad (for us), and when it is being good

Friction, such as air resistance slows objects down

But it is not always bad - you and your partner now need to write down some examples of friction when it is being bad (for us), and when it is being good

Friction - badFriction - bad Air resistance slows vehicles down, so the engine needs

to propel them (it must work harder at higher speeds)

Friction makes it difficult to swim through water quickly

Friction causes wear and heating - machines which have parts which touch / slide over each other produce lots of heat and wear - meaning they need lubricants

Air resistance slows vehicles down, so the engine needs to propel them (it must work harder at higher speeds)

Friction makes it difficult to swim through water quickly

Friction causes wear and heating - machines which have parts which touch / slide over each other produce lots of heat and wear - meaning they need lubricants

Friction - goodFriction - good Air resistance slows vehicles down, which can be

very useful for vehicles such as the space shuttle which use the Earth’s atmosphere to slow it down, allowing it to land

Parachutes utilise air resistance to slow people down, when falling to Earth

If there wasn’t any friction we couldn’t slow our bikes down - brakes utilise friction to our advantage

We wouldn’t be able to move without friction - just as low friction surfaces such as ice as hard to walk on, no friction would be impossible!

Friction holds nuts and bolts together etc…

Air resistance slows vehicles down, which can be very useful for vehicles such as the space shuttle which use the Earth’s atmosphere to slow it down, allowing it to land

Parachutes utilise air resistance to slow people down, when falling to Earth

If there wasn’t any friction we couldn’t slow our bikes down - brakes utilise friction to our advantage

We wouldn’t be able to move without friction - just as low friction surfaces such as ice as hard to walk on, no friction would be impossible!

Friction holds nuts and bolts together etc…

QuestionQuestion Why is it harder to run through water, than it is to

run through the air?

Answer this question using your new knowledge of friction

If you finish this, can you think of ways we could get through the water more quickly (using scientific ideas)

Why is it harder to run through water, than it is to run through the air?

Answer this question using your new knowledge of friction

If you finish this, can you think of ways we could get through the water more quickly (using scientific ideas)