Lesson video

(no audio) <v ->Hello everyone.

How are you doing today?

</v> Hope you're feeling really good.

My name is Ms. Afzal and I'll be your teacher for this lesson.

I'm feeling really pleased about that because we've got such an interesting topic ahead.

We're gonna be looking at surfaces.

Our lesson is called different surfaces in real life.

And we'll be looking at what kinds of surfaces are useful for different purposes.

I hope this all sounds of interest to you.

A lesson comes from the unit of work, simple forces, including magnets.

So if you are ready with some interest, energy, and enthusiasm, we'll begin our lesson now.

The outcome for today's lesson is I can explain why some surfaces are suitable for different jobs and give examples from real life.

I hope that sounds interesting to you.

We have some keywords in today's lesson and I'd like us to go through them one at a time.

My turn, your turn.

Are you ready?

Here's our first word, frictional forces.

Surface Grip.

Properties.

I liked hearing those keywords loud and clear.

Let me say them one more time.

We have got frictional forces, surface, grip and properties.

Pause here and share with someone.

Have you heard of any of these words before?

Thanks for sharing and don't worry whether you've heard of these words or whether you haven't.

We are gonna go into each of them.

We'll find out more about what these words mean.

So frictional forces are forces that act between the surfaces of objects.

The surface is the top or the outside layer of an object or material.

A grip is a firm hold or a tight grasp.

And materials properties are its qualities such as how hard or soft it is or whether it is rough or smooth.

So these are our keywords, frictional forces, surface, grip, and properties.

Let's look out for these words.

Let's listen out for them.

Let's think carefully about these keywords.

They'll be coming up in today's lesson.

Our lesson today is called different surfaces in real life.

And it has three learning cycles.

First of all, frictional forces can be useful.

Next, frictional forces can be unhelpful.

And then, frictional forces can create heat.

Let's begin with the first learning cycle.

Frictional forces can be useful.

Have you ever tried to walk on ice?

Take a look at that picture of an icy road.

Have you ever walked somewhere like this before?

Pause here and share with someone?

Have you tried to walk on ice and what was it like when you tried?

Thanks for sharing.

Ice is difficult to walk on because it is very smooth.

A smooth surface does not create much grip with our shoes.

We need frictional forces to be able to walk without slipping.

Yeah, is that what happened to you?

Did you slip?

I know.

It can be painful when you slip on ice.

How do rock climbers use fictional forces to grip the surface of the rock?

Pause here and share with someone?

How do you think they do this?

Thanks for sharing.

Rock climbers often wear shoes with rubber soles.

We can see a rock climber there with their rubber sole shoes.

An important property of this material is that it creates high frictional forces with the surface of the rock.

So the rock climber is able to grip onto the surface of the rock.

Goalkeepers need to be able to grip onto a ball to stop goals being scored.

Their gloves are made using fabric that has properties suitable for creating high frictional forces with the surface of the ball.

Oh my goodness, I think this must be my favorite page yet because we have got all four of our keywords on this one page.

We have grip, we have properties, we have frictional forces, and we have surface.

Can you think of other examples where frictional forces are useful?

Pause here and share with someone.

Thanks for sharing your ideas.

How are frictional forces helpful in the images below?

Pause and share with someone.

What frictional forces can you see here and how are they helpful?

Thanks for sharing.

Perhaps you said that frictional forces allows bikes and cars to go around corners.

How about in this image?

Can you see frictional forces being helpful?

Pause here and share with someone.

Frictional forces allows us to hold pencils.

And finally, take a look at this image.

How are frictional forces helpful in this image?

Pause here and share.

Frictional forces allows us to grip bats just like this cricket player.

Let's have a check for understanding.

Frictional forces helps us to, onto surfaces.

Pause here and share with someone.

What's the missing word in this sentence?

Well done if you said grip.

Frictional forces helps us to grip onto surfaces.

Let's have another check for understanding.

Which two of these are made easier by frictional forces?

A, holding a cricket bat.

B, sliding down a slide.

Or C, doing a handstand.

Pause here and share with someone.

Well done if you selected answers A and C.

Indeed, holding a cricket bat and doing a handstand are made easier by frictional forces.

And now pause here and share with someone.

Can you explain why?

Thanks for sharing.

It's now time for your first task.

Your local football team need to find the best fabric for goalkeeping gloves.

First of all, I'd like you to talk about what properties a fabric used for goalkeeping gloves needs to have.

And then think about how you can explore and test different fabrics for goalkeeping gloves.

Pause here while you have a go at these two parts of your task.

I'll see you when you're finished.

It's good to be back with you.

So how did you get on with that task?

First of all, talking about the properties of goalkeeping gloves.

Perhaps you said something like this.

Here's Andy.

I think the surface of goalkeeping gloves needs to be rough and bumpy so that there is greater friction force and more grip.

I like your thinking, Andy.

And how did you get on thinking about how you can explore and test the fabrics?

Here's Lucas, I will feel how easy it is to move the fabrics across each other.

And Sam, I will slide the fabrics over a smooth surface.

I like these ideas, and well done for coming up with yours.

And I wonder, do you have other ideas or were your ideas the same as Lucas's and Sam's?

(no audio) Thanks for sharing.

And now for the next part of your task, I will let you to explore and test the fabrics for goalkeeping gloves.

Feel the different fabrics.

Put on a pair of the gloves and see how easy it is to move the palms of your hands over each other.

Wearing the gloves, how easy or difficult is it to pick up or catch a smooth ball?

So pause here while you have a go at testing the fabrics for goalkeeping gloves.

I'll see you when you're finished.

Good to be back with you.

How did you get on, exploring and testing the fabrics how they feel?

You might have found the same things as Lucas, Sam, and Andy.

Here's Lucas, the wool gloves felt soft and had bobbly bits.

Andy, the toweling gloves felt rough on my fingers.

And Sam, the gloves made from bin bags were smooth.

How about moving gloves over each other?

Lucas found that the wool gloves could move over each other easily.

But the toweling gloves took more effort.

And Andy, the toweling gloves kept sticking together.

But when I wore the bin bag gloves or the wool gloves, it was easy to move my hands over each other.

And how did it go picking up or catching a ball?

Andy, it was really hard to catch the ball when I wore the bin bag gloves because they kept slipping.

They wouldn't make good goalkeeper gloves because they don't create much fictional force.

Lucas, the toweling gloves would make the best goalkeeper gloves because they didn't slip when I tried to pick up the ball.

They created the most frictional forces with the ball.

And now we're onto our next learning cycle.

Frictional forces can be unhelpful.

If there's too much friction force it is difficult for an object to move over a surface.

How easily would this car drive in deep mud?

And how easily would a ball roll through this long grass?

Pause here and share with someone.

What do you think?

Thanks for sharing.

Yeah, it probably wouldn't be very easy to drive in that deep mud or to roll a ball through this long grass.

How are frictional forces unhelpful in these examples?

Pause here and share with someone.

Thanks for sharing.

Frictional horses can cause surfaces to wear away.

How have these surfaces been worn away by friction?

The sole of a shoe and a bicycle tire.

Pause here and share with someone.

Thanks for sharing.

Have you ever been injured by frictional forces?

Pause here and share with someone if you have.

Thanks for sharing.

If you fall on a rough surface like the playground, it is frictional forces that wear your skin away, giving you a graze or a cut.

I've certainly come across a grazed knee or elbow in the playground.

In engines and other machines, frictional forces can wear away important parts.

To make the moving parts of machines, engineers select materials with properties that reduce friction and help surfaces to move over each other more easily.

We can see the fascinating inside of the machine there.

Let's have a check for understanding.

Which two of these statements are true?

A, frictional forces can wear away surfaces.

B, frictional forces can make it difficult to move.

C, frictional forces can make things heavier.

Pause here while you decide which two of these statements are true.

Well done if you selected statements A and B.

Indeed, frictional forces can wear away surfaces and frictional forces can make it difficult to move.

Let's have another check for understanding.

For skateboarding, frictional forces can be helpful and unhelpful.

Match the endings to the correct sentence starters.

So here are our sentence starters.

Friction can be unhelpful for skateboarding because?

And friction can be helpful for skateboarding because?

And our endings, it slows down objects moving over a surface so the skateboard can stop.

More effort is needed to make the wheels move across the surface.

Pause here while you match the correct sentence starters and endings.

Well done if you connected the sentence starters and endings in this way.

And now it's time for your next task.

Laura and Jacob are discussing which properties of a material would be best for the sole of a sports shoe.

Here's Laura, it should be made of a material that creates low frictional forces, so you don't have to work hard to run.

And Jacob, it should be made of a material that creates high frictional forces to stop you slipping on the floor.

Who do you agree with and why?

Have a discussion with someone about this.

I'll see you when you're finished.

It's good to be back with you.

So who did you agree with and why?

Well, they're both correct.

For some products like sports shoes and tires, materials are needed that offer enough grip so you don't slip, but not too much grip that you can't move.

Well done if you discussed something like this.

And now it's time for our final learning cycle.

Frictional forces can create heat.

Frictional forces can create heat.

Sometimes this heat can be useful.

Frictional forces can create fire.

Rubbing these sticks together.

It's gonna help to create a fire.

Frictional forces create the heat needed to light a match.

Sometimes heat created by frictional forces can be unhelpful.

Frictional forces between surfaces and engines can make them overheat and stop working.

Frictional forces between moving plastic parts in machines can cause them to melt.

Oh my goodness.

And take a look at this image of some of the moving parts of an engine.

A lot of frictional forces at work there.

To prevent dangerous levels of heat in machines, engineers sometimes add oil or grease between surfaces because they can reduce frictional forces.

Cyclists add oil to the gears on their bikes to reduce frictional forces.

Oil and grease allow surfaces in moving machine parts to slide smoothly past each other.

Let's have a check for understanding.

When you rub two sticks together, something, forces can create heat and make the sticks burn.

Pause here and share with someone, what word is missing from this sentence?

Well done if you added the word friction.

When you rub two sticks together, friction forces can create heat and make the sticks burn.

Let's have another check for understanding.

True or false?

It's not always helpful that frictional forces create heat.

Pause here and decide.

Is this true or false?

(no audio) Well done if you selected true.

And now I'd like you to give some reasons for your answer.

So either, I think it's because A, when frictional forces heat up the moving parts in engines, it can cause overheating and damage.

Or B, when frictional forces heat up the moving parts in engines, they work better.

Pause here while you choose.

Well done if you selected statement A.

And now it's time for your next task.

You are going to investigate frictional forces between the surfaces of your hands.

So first of all, rub the palms of your hands together for 10 seconds.

Describe how they feel and why do they feel like this?

So pause here while you have a go at this first part of your task, rubbing your hands together for 10 seconds, describing how they feel, and then considering why it is they feel this way.

I'll see you when you're finished.

And now the next part of your task.

I would like you to put a small blob of hand cream on the palm of one hand.

Now rub the palms of your hands together again for 10 seconds.

Do you observe any difference in how your hands felt with and without the hand cream?

And why do you think this was?

Now pause here while you have a go at this next part of your task, putting a small hand cream on a palm of one hand and rubbing your palms together and observing the difference and considering why this was.

I'll see you when you're finished.

It's good to be back with you.

How did you get on with that task of investigating frictional forces between the surfaces of your hands?

Here's Aisha, after I rub my hands together, they felt warm because rubbing them together created frictional forces between them and this creates heat.

And Sam, when I rubbed my hands together with the hand cream, they didn't feel as warm.

The hand cream reduced the frictional forces between my hands, so less heat was created.

I wonder, were your observation similar or different.

Pause here and share with someone.

Thanks for sharing.

In our lesson, different surfaces in real life, we've covered the following, friction can be a useful force.

It can help us grip so we can walk and hold onto things.

Friction can be an unhelpful force.

It can wear away surfaces and make it difficult to move.

Scientists, designers and engineers choose materials that have suitable properties for their work or products.

Frictional forces can create heat.

Well done everyone for joining in with this lesson.

It was great to explore different surfaces, frictional forces, and how they can be helpful or unhelpful.

How we can use our knowledge of frictional forces to help us choose appropriate materials for different tasks and products.

Well done for joining in, experimenting, observing, investigating, and I'm looking forward to seeing you at another lesson soon.

Until then, stay curious.