Hi, everyone.

Welcome to our science lesson.

I'm Dr.

Pemberton, and I hope you are looking forward to doing some science.

I am.

So let's get going.

Today's lesson is called How Gears Can Help Us.

Do you know what a gear is? Do you think you've seen one anywhere today? The learning outcome for today is that you can describe how gears can make difficult work easier.

It's part of our big question, how do forces make things happen? Hopefully we'll have some fun today while we learn about gears together.

These are the key words that we'll be using in today's lesson.

Gear, cog, axle, and force.

Some of these words are new today, but I'm sure some of them are already familiar to you.

This slide shows the meaning of each of the keywords.

I'll explain the words as we come across them during the lesson, so I won't read each of them now.

It is here as a reminder there if you want to come back to it later and check whether you've understood correctly.

This is our lesson outline for today.

There are three parts to the lesson.

We'll begin by learning that gears are simple machines.

Then we'll be investigating gears, and finally, we'll learn how gears can help us.

We're going to get going on the first part of our lesson now.

Gears are simple machines.

Simple machines are tools that can make difficult jobs easier.

Some machines help us to lift things.

On the left here, we can see pulleys on a boat, and on the right we can see a seesaw, which is a type of lever.

These are both simple machines, and they both help lift things.

Other machines are useful for making things turn, like the hands on a clock or an electric drill.

Do you know what these simple machines are called? Gears are simple machines or mechanisms which are useful for turning things.

You may have heard of gears on a car or on a bicycle.

Lots of other machines use gears to help them turn things.

Gears are flat wheels with teeth which stick out and have gaps in between.

In the pictures you can see that each of the sticking outfits is called a tooth.

So a gear is a toothed wheel.

These types of wheels are sometimes called cogs.

The teeth of different gears fit together.

Here you can see a gear system with at least 12 different cogs.

This white box on the picture shows a section where the teeth of two gears slot together.

They turn on an axle, which is a rod that goes through the centre of the wheel, and you can see one of these shown down on the left-hand side of the picture with the white line.

When one gear turns, it turns the other interlocked gear too.

This means that the effort used to turn the first wheel also causes the second wheel to turn.

In the picture, you can see that using effort to turn the left-hand wheel causes the second right-hand wheel to turn because of the force produced.

Let's check what we've learned so far by trying a couple of questions.

This one's a multiple choice question.

It says, "Gears are simple machines useful for.

." Is it A, balancing things? B, lifting things? C, turning things? Well done if you chose C, turning things.

So the whole sentence is gears are simple machines useful for turning things.

Let's try another one.

Look at these photos.

Which of these images shows a toothed wheel? Is it A, B, or C? That's right, it's A and B.

Image C shows a steering wheel, which is a wheel but doesn't have a toothed edge.

Let's try one more.

This one's a true or false question.

Is it true or false that gears can change the direction of a force? That's right.

It's true.

Can you justify your answer? Do you think it's true because gears move horizontally and vertically? That's A or B, because gears turn clockwise and anti-clockwise.

That's right, it's B.

Gears turn clockwise and anti-clockwise.

Well done if you got that right, and don't worry if you didn't, because it's your turn to do some science now, and this will help your understanding, I'm sure.

This is your first science challenge for the day.

You are going to explore gears with Izzy.

If you have a gears kit, use that, but if not, you will need to make some gears.

I'm going to show you how to make one of the gears.

The first job is to draw a circle about 10 centimetres in diameter on stiff cardboard and cut it out so you get a circle like this.

Then do the same with a piece of paper.

Next, take a lollipop sticks like this and cut them in half.

So you will end up with 16 pieces of lollipop stick just like this.

Now your next job's a bit fiddly.

You need to use some glue and stick your lollipop sticks all the way around the outside of your wheel, and you need to spread them out so they're evenly spaced, and you want 'em to stick out about 2 1/2 centimetres beyond the edge of the wheel.

When you've done that, it should look like this.

And now you need to take your piece of paper and stick that over the top.

So I've got my gear, but to use it, I need an axle as well that goes through the middle, and I need to attach it to a base on which it can turn.

So the next stage, which you might need adult help for, is to take a cocktail stick that's had one of the sharp ends cut off it, and push it through your gear like this.

You can see it's poking all the way through.

Then you poke the end of your gear into some blue tack, and then you can rest it on the desk and it should turn.

When you've made both of your gears, place them next to each other on the table so that the teeth interlock.

Now, once you have your gears, explore them.

What happens if you turn one gear? Does the other gear turn in the same direction? Or if you added a third gear or even more, in which direction would that turn? Off you go and try these activities.

Then come back when you are ready to move on to the next bit of the lesson.

Welcome back.

How did you get on and what did you find out? You might have found something like this.

So you had to explore your gears, and you might have observed something like this.

These children said, "When we turned one gear, the other gear moved in the opposite direction." Another one said, "With three gears, when we turned one gear, one moved in the opposite direction to that.

Then the third gear moved in the same direction as the first gear." And finally, "The fourth gear moved in the same direction as the second one." So each gear turned in the opposite direction to the ones it was next to.

I expect you found that too.

Did you notice? Now we're gonna move on to the second part of our lesson, and we're gonna be doing a bit more work investigating gears.

Andy investigates two gears the same size.

If the first gear on the left turns anti-clockwise, then the second gear on the right turns clockwise.

He observes that when one gear is turned, the other gear turns in the opposite direction, just like we found.

Andeep says this means that gears can change the direction of a force.

Well spotted, Andeep.

Andeep makes another observation.

He says that when the gears are the same size, the second gear turns at the same speed as the first gear with the same force.

Andeep has seen gears of different sizes in some machines.

He wonders if different sized gears can be used to change the speed and reduce the force, the effort, required to turn things.

Andeep talks to his friend Sophia about this.

They both have different ideas about gears.

Sophia says, "I think small gears will turn quickly, so we'll create a bigger force to turn things." But Andeep says, "I think larger gears will turn slowly and create a bigger force to turn things." What do you think? Let's try a few questions to see how we're getting on.

When two gears of the same size are used, how does the turning force of the second gear compare to the first gear? Do you think A, it's less? B, it's the same? Or C, it's more? That's right, it's B.

When two gears of the same size are used, the turning force of the second gear is the same as the turning force of the first gear.

Let's try another one.

If you have three gears in a row, does the final gear move in the same or opposite direction as the first? Do you think it's A, the same, or B, the opposite? That's right.

It's A, the same direction.

With three gears, the final gear moves in the same direction as the first.

Now it's time for you to do some more science.

You're going to carry on exploring gears with Izzy.

She's going to use a gears kit again, but you might choose to use homemade gears.

If you are using homemade gears, you need to make one more gear now in the same way you made them before, but this time your new gear needs to be bigger.

It needs to be 15 centimetres in diameter.

If you're going to make a gear, go away and do that now and then come back to find out what to do with it.

Okay, so you need to mark one of the teeth on each of your gears.

I've got my gear here.

I'm going to put a cross on one of the teeth.

So now I'll always know which gear it is.

Now this is because it makes it easy to see when the gear has made one complete turn.

So now your challenges.

The first one is for you to turn the small wheel one complete turn.

And then see, has the large wheel turned less than, equal to or more than one complete turn? Now you need to place one large gear and one small gear next to each other just like in task A, so that when you turn one of them, it makes the other gear turn.

First of all, turn the small wheel one complete turn.

And have a look to see, has the large wheel turned less than, equal to, or more than one complete turn? Next, try the other way.

Turn the large wheel one complete turn.

This time, has the small wheel turned less than, equal to, or more than one complete turn? Pause the video now and go and try this, and then come back and join me.

How did you get on? You might have found something like this.

So you were investigating how gear size affects the speed of the turn.

With the first challenge, Izzy said, "When we turned the small gear one complete turn, the large gear turned less than one complete turn." And with the second challenge she noticed, "When we turned the large gear one complete turn, the small gear turned more than one complete turn." Hopefully you spotted that too.

Well, we've come to the final part of our learning now.

We're going to see how gears can help us.

If you use a small gear to turn a larger gear, the larger gear will turn more slowly and with more force than the first smaller gear.

So if you turn the smaller gear, the larger gear turns more slowly with more force.

If you use a large gear to turn a smaller gear, the smaller gear will turn more quickly and with less force than the first gear.

So you turn the larger gear, and then the smaller gear turns more quickly and with less force.

Let's do a quick understanding check to see how we're getting on.

This question's a gap filled with two missing words.

Which two words should fill these gaps? Gears can be used to change the blank, speed, and blank of a force.

Should we replace the blanks with A, direction, B, pressure, or C, size? That's right.

It's A, direction and C, size.

So the whole sentence is gears can be used to change the direction, speed and size of a force.

Let's do a bit more learning.

Bikes have gears.

On a bike, the two gears do not touch each other directly.

Instead, they're joined by a chain which slots over the teeth.

Now in this fantastic moving diagram, you can see this.

As it turns around, the teeth on the cog slot into the next bit of the chain and pull it round.

Bike gears allow us to use the effort of our legs to push the pedals to make the wheels turn, just like the cyclist in this photo.

Having gears of different sizes helps us change speed and effort depending on whether we are cycling uphill, downhill, or on a flat path.

Here we can see a cyclist peddling uphill in a low gear.

So if you're using low gears on a bicycle, it means that you turn a smaller gear, and the larger gear turns very slowly.

More force is produced in the larger gear, so pedalling is easier.

The bicycle goes slower, and this helps when we're going up a hill.

But if you're using a high gear on a bicycle, that means that you turn a larger gear, and the smaller gear turns very quickly.

Less force is produced, so pedalling is harder, but the bicycle goes faster, and this is really good when riding on smooth, flat ground.

And here we can see the cyclist in the diagram pedalling on smooth, flat ground in a high gear.

Let's see what you've learned by trying our final knowledge check for this lesson.

This one's a multiple choice question.

Which of these everyday items uses gears? Is it A, clocks, B, scissors, or C, window blinds? That's right.

It's A, clocks.

Scissors are levers, and window blinds use pulleys.

Let's try our last one.

This one is a true or false question.

If you use a small gear to turn a larger gear, the larger gear will turn with more force than the first smaller gear.

Is that true or false? That's right.

It's true.

But can you explain why? Is it because A, the larger gear will turn more quickly and with more force than the first smaller gear? Or is it because B, the larger gear will turn more slowly but with more force than the first smaller gear? That's right.

It's B.

The larger gear will turn more slowly, but with more force than the first smaller gear.

Now it's time for your final task.

Jacob, Izzy and Laura are talking about gears.

Jacob says, "To change the speed and power of a turning force, you should use gears which are different sizes to each other." Izzy says, "A larger gear turns quickly with less force, but a smaller gear turns more slowly with greater force." And Laura says, "A smaller gear turns quickly with less force, but a larger gear turns more slowly with greater force." Who do you agree with and why? Use a set of gears to help you explain.

Go and think about that now and pause the video while you explain it to somebody, and then come back for the final part of our lesson.

Well, Jacob and Laura are both correct.

As Jacob said, it's true that to change the speed and power of a turning force, you should use gears which are different sizes to each other.

And as Laura said, it is also true that a smaller gear turns quickly with less force, but a larger gear turns more slowly with greater force.

Well, we're coming to the end of our learning, so let's look at the summary to remind ourselves what we have learned today.

Gears are simple machines which are useful for turning things.

Gears are wheels with teeth that slot together and turn on an axle.

Gears can change the direction of a force.

Gears allow a smaller force to have a greater effect.

A smaller gear will turn rapidly with less force, whereas a larger gear will turn more slowly with a greater force.

Thank you for joining me this lesson.

We finished learning about gears now, and I've really enjoyed myself.

I hope you have too.

Why don't you look out for gears over the next few days? Perhaps you'll find one in a place I haven't mentioned.

Well done for your hard work, and have a great day.