Hello, my name is Mrs. Mehrin and I am so excited today to be learning all about water resistance and planning an investigation with you.

We are going to do brilliantly.

Welcome to today's lesson from the unit Forces, including simple machines.

Your learning outcome for today is I can plan an investigation to identify the effects of water resistance.

Now, I know that sometimes learning can be a little bit challenging, but that's okay because we're going to work together and we are going to have a great time learning lots of new things.

Now we're going to be building on some of your previous knowledge all about water resistance.

Here are your keywords for today.

You can pause the video if you'd like and write them down.

However, I will be going through these words throughout the lesson, so if you'd like to pause the video and jot them down, you can do now.

Fantastic.

And here are the definitions for those words.

Again, I will be going through these throughout the lesson and you can always come back to this part of the lesson if you'd like.

So there's no need for you to pause the video and jot these down, but if you would like to do so, please do that now.

Fantastic, well done.

So our lesson today is split into two parts.

Let's begin with the first one, water resistance.

Have you ever tried to walk in a swimming pool full of water? And can you remember how it felt? Can you mime how you would walk through a swimming pool? And why is walking through water different to walking through air? So there's lots of questions there for you to have a really good think about.

So I'd like you to pause the video here and just have a go at answering those questions.

Off you go.

Fantastic.

Well done.

So you may have said that walking through a swimming pool full of water is much more difficult than walking through air.

Now we are going to find out why that is.

Friction acts between surfaces and can slow down objects or prevent them from moving.

Air resistance is a type of friction force that acts between air and moving objects, just like in this diagram here.

But what happens in water? I'd like you to think about that question.

I'll give you five seconds to think about your answer, but if you need longer, you can pause the video here.

Off you go.

Fantastic, well done.

Now I'd like you to also think about this question.

Do you think there's any friction in water? So air resistance is type of friction, and we have frictions acting between surfaces that can slow down objects or prevent them from moving.

But what about in water? Do you think there might be friction there? I'd like you to think about that question.

I'll give you five seconds, but if you think you need longer, you can pause the video here.

Off you go.

Fantastic.

Well done.

So here is a picture of a boat moving through water and it says when objects move in water, or in any liquid, they have to push the water in front of them out of the way.

The water hits the surface of the object and creates a force.

And this force is called water resistance.

Now, water resistance is a type of friction force which acts between the water and the surface of the object, and it acts in the opposite direction to the movement of the object through the water, which slows down the moving object trying to get through the water.

Now, that is the reason why it is more difficult to walk through water than it is to walk through air because you have all of that water resistance there trying to prevent you from being able to get through or slowing you down.

So here we have a fish and the fish swims forward, but the water resistance is acting in the opposite direction, trying to stop it or trying to slow it down.

Water resistance affects objects moving horizontally through water, and it also affects objects falling down through water like this pebble.

Gravity pulls the object down and water resistance acts in the opposite direction and slows down how quickly it's going to sink.

Now let's do this question to check your understanding.

So something is a force that acts to slow down or stop objects that are moving through liquid.

The water hits the something of the object and creates a force.

So I'll give you five seconds to think about your answer, but if you think you're going to need longer, you can just pause the video here.

Off you go.

Fantastic.

Well done.

Let's see if you are correct.

Water resistance is a force that acts to slow down or stop objects that are moving through liquid.

The water hits the surface of the object and creates a force.

Well done.

Let's do one more question together.

It says, in which direction does water act on a moving object? So in which direction does water act on a moving object? So is it A, the same as the movement, B, downwards, C, in all directions, or D, opposite the movement? So I'm going to give you five seconds to think about your answer, but again, if you need longer, just pause the video here.

Off you go.

Fantastic.

Well done.

The answer is opposite the movement.

So here is your first task, task A.

Alex, Jacob and Sophia are discussing walking in water, and they've all noticed that it's harder to walk in water than on land.

Alex says, "This is because the water feels cold and that makes you move more slowly than on land." Jacob says, "Water pushes against you to slow you down, but there is no resistance when walking on land." And Sophia says, "There is more resistance when walking through water than through air." Who do you agree with and why? So I'll give you some time.

I'll give you five seconds to think about your answer.

But if you need to pause the video and reread the statements, that's absolutely fine and you can pause the video here if you need to.

Off you go.

Fantastic.

Well done.

The correct answer is Sophia.

Sophia is correct.

She said there is more resistance when walking through water than through air.

So there is resistance in both air and water because you have air resistance and water resistance, but it is greater in water as the particles are closer together and this is why it feels hard to push through the force of water.

Now we're onto the second part of our learning today, which is scientists plan investigations into water resistance.

So we have Lucas, Laura, and Sam, and they are all thinking about water resistance.

They're trying to come up with a question that they can investigate with a fair test investigation, and they realise that not every question can be answered with an investigation.

Lucas says, "What is the best thing about water resistance?" Laura says, "Why does water resistance exist?" And Sam asks, "When is water resistance helpful?" The children want to ask a question that they can investigate with a fair test.

That means they need to be making observations or taking measurements, and they ask the question, does the shape of an object affect its water resistance? They plan to make different shaped rafts using polystyrene packaging, and the children want to use a fan to propel their rafts along a water channel and to time how long it takes.

So here we have a diagram to show what their investigation would look like.

So you have a fan blowing through this water channel.

You've got the raft made out of polystyrene packaging, and you have the water channel filled with water.

The children have made their channel using an old length of gutter and they want to work scientifically and make their test as fair as possible.

What variables could they change in their investigation? So I'd like you to pause the video here and just have a really good think about the variables that they might change in their investigation.

Off you go.

Fantastic.

Well done.

So the variables could include the mass of the rafts, so how heavy they are, how light they are, the shape of the rafts, the length of the water channels.

So maybe it's gonna be really long, could be really short.

The amount of water that they put in because that's going to affect the amount of water resistance as well, that you have.

The strength of the fan.

And was there anything else that you might have thought of? Now I want you to think about which variables they should change.

So I'm going to give you five seconds here, or if you need to go back over those statements, that's absolutely fine.

You can pause the video here and have a go at doing that.

Off you go.

Fantastic.

Well done.

So the children have decided they're only going to change the shape of the rafts.

All the other variables are going to be controlled or they're going to be kept the same, and their rafts are identical to each other except for the shape of the front ends.

So Lucas's raft has a circular end, so it's flat and circular.

Laura's raft has a square end and Sam's raft has a triangular end.

So Sam has thought of another question to investigate about water resistance, and Sam says, "Does the shape of an object affect the time it takes to fall vertically through water?" And she's wondering how to plan this.

What is Sam going to need and what will she do to make sure that it's a fair test investigation? So think about what we just did with the other question.

How did we come up with a fair test investigation? So I'd like you to pause the video here so you can have a really good think about this question and then come back to our lesson once you have, off you go.

Fantastic, well done.

So let's have a check-in quickly before we carry on with our learning just to make sure that we've understood what we've learned so far.

So this question says, what does it mean if you control a variable? Does it mean that you keep it the same each time you do the test? Or does it mean that you change it each time you do the test? So I'll give you five seconds to think about your answer, but if you need longer, just pause the video here and come back to the lesson once you're ready, off you go.

Fantastic, well done.

The answer is that you keep it the same each time you do the test.

So that is you controlling a variable.

Now, if you make rafts to answer the question, does the mass of an object affect its water resistance? Which of these variables should you change in your investigation? Should you A, change the length of the water channel, B, the shape of the rafts, C, the mass of the rafts, or D, the amount of water in the channel? So I'll give you five seconds to think about this answer, but if you do need longer, that's absolutely fine.

You can pause the video here and then you can come back to the lesson once you are ready.

Off you go.

Fantastic, well done.

The correct answer is C, the mass of the rafts.

So here is your task B.

It says, plan an investigation to answer this inquiry question.

Does the shape of an object affect the time it takes to fall through water? So your equipment that you're going to need is a large two litre bottle of water, three lumps of modelling clay of equal size, a stopwatch.

Now, what could you do to test whether or not the shape of an object affects the time it takes to fall through water? I'll give you some time to think about that question.

I'll give you five seconds, but if you need longer, that's absolutely fine.

Just pause the video and come back to the lesson when you're ready.

Off you go.

Fantastic, well done.

So the first thing that you need to do is think about what the variables are.

So you're going to discuss and then record your plan as a series of numbered steps.

You're going to include a drawing of the shapes that you're going to test, explain which variables you will control and which you will change.

So what I'd like to do now is pause the video here, use this page to help you to come up with your plan for your investigation.

So think about those variables.

Record your plan as a series of number steps.

Include a drawing of the shapes you're going to test and explain which ones, which variables you're going to control and which you're going to change.

So I'd like you to pause the video here and have a go at that activity.

Off you go.

Fantastic, well done.

So remember when you are doing this activity and you are looking at number three where it says, explain which variables you're going to control and which of those that you are going to change.

Remember, you are just changing one variable and everything else in your test, all the other variables that they are just being, they are being controlled.

So you're keeping them the same because we just want to work with changing one variable at a time to ensure that we've got a fair test.

So your plan may have looked like this.

Make each of the pieces of modelling clay into different shapes like this.

So you've got cube, thin cylinder, flat disc.

Drop each piece of modelling clay into the two litre of bottle of water with the top cut off and time how long it takes to reach the bottom and change the shape of the modelling clay each time keeping its mass, so how much it's weighing constant.

You're also going to control the size and shape of bottle and the amount of water.

So if we go through, just go through some of these together.

Now remember, this is just what your plan might have looked like.

You may have chosen to do different shapes.

You don't have to choose a cube or a cylinder or a flat disc.

These are just some examples.

You may have chosen a pyramid shape, you may have chosen a triangular shape.

You may have chosen a completely different shape.

Now, when you drop each piece of your modelling clay into the two litre bottle of water, you also need to decide how much water you are going to have in that two litre bottle of water.

Whether or not you're going to fill it right up to the top or maybe slightly less than that.

But remember how much water you decide to use is how much water you need to keep for every single shape, because the only thing that you are changing here is the shape of the modelling clay.

The mass, so the weight of your modelling clay needs to stay the same.

The shape and size of the bottle and the amount of water, all of that must remain the same in order to make this into a fair test.

So let's go over our summary for today.

Water resistance is a force which acts to slow down or stop objects that are moving through liquid.

Water resistance acts in the opposite direction to a moving object.

Water resistance is stronger than air resistance.

Scientists ask questions about water resistance to help them to find out more about it, and scientists control variables and plan fair tests to investigate the water resistance.

Well done for today.

You have worked so incredibly hard.

There has been a lot of new learning for you today, but you've done brilliantly.

Fantastic learning.

Well done.