Hello, everyone.

It's lovely to be learning science with you today.

I'm Dr.

Pemberton.

I'm called Dr.

Pemberton, but I'm not a medical doctor.

I'm a doctor of science, which means my special subject is science rather than medicine and helping ill people.

I'm looking forward to working through the lesson with you, so let's get going.

Today's lesson is on contact forces, and our learning will build on what you already know about materials and movement.

The learning outcome for today is that you can observe that some forces need contact between two objects and also that you'll be able to give examples of contact forces from real life.

It's part of our big question, how do forces make things happen? I think you'll find that, without realising it, you're probably already a bit of an expert on this topiC, as you've been using forces all of your life.

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

Force, push, pull, contact force, and Venn diagram.

Here are the explanations showing what each of the keywords mean.

I'll explain these words as we come across them during the lesson, so we won't spend time going through each one now.

It's just here as a reminder, and you might like to come back to it later to check that you are confident with using each of those keywords.

Here's our lesson outline for today.

There are three parts to the lesson.

We are going to get going on the first part of our lesson now as we think about the question, what are forces? So my first question to you is, do you know what forces are? Perhaps you have an idea in your head already.

Perhaps forces is a word you've heard before, maybe on TV, or maybe you've seen it in a book.

These photographs might help.

They all show forces and they might help you decide what the word means.

This little child is using a force.

There are lots of forces in this picture.

An important force is about to happen when the baseball batter hits the ball.

In this photo, the baker is using a force on the dough.

All of these photos show things that forces can do.

Forces are amazing and can cause different things to happen.

If we go back to the first photo of the child with the walker, this is an example of how forces can make things move.

With the baseball photo, when this batter hits the ball, the force will make the ball change direction.

Forces can also make things slow down, like when another player catches the ball that the batter is about to hit.

In our final photo, when the baker kneads the dough, the force makes the dough change shape.

Things start to move when a force acts on them.

Here is a wooden cart on wheels.

It can't move on its own.

This cart moves only if something or someone pushes or pulls it.

Pushes and pulls are forces.

Let's think about some examples of pushes and pulls.

A push moves objects further away.

Have you pushed a door shut today? A pull brings objects closer.

I wonder if any of you have pulled open a drawer today.

What pushes and pulls have you done today? I pulled open my closed drawer to get out my jumper this morning and I pushed the door shut after I'd come into this room.

Let's look at some more examples of forces in use.

What forces are being used here? You can squash something using a push force.

You can stretch something using a pull force.

You can twist something using pushes and pulls.

Try those actions as you say them.

Squash, stretch, twist.

Let's check what we've learned so far by trying some questions.

Which of these forces are pushes and which are pulls? Using a doorbell, tying a shoelace, throwing a snowball, and catching a tennis ball.

That's right.

When we use a doorbell, we push.

When we tie our shoe laces, we pull.

When we throw a snowball, we push.

And when we catch a ball, like a tennis ball, we pull it.

Can you mind catching a ball to feel how your hands come down into your body just when you pull something? Let's try a second question.

Is this true or false? When you throw a basketball, you use a push force.

You might like to mind the action to help you decide.

That's right, it's true.

Can you explain why you think it's true? Do you think it's true like A, because forces involving balls are always pushes? Or do you think it's true like B, because it counts as a push and a contact force even if you only touch the object for a short amount of time? That's right.

It's B.

It counts as a push even if you only touch the object for a short amount of time.

Now it's your turn to do some science.

This is your first science challenge for the day.

Are you feeling confident? I think you're ready for it.

You are going to see some photos involving forces.

For each photo, you'll need to decide whether your use a push or a pull force to do the action or make the item work.

Okay, here we go.

Let's see, our first one.

A tug of war.

Next one.

Moving forwards on a skateboard.

And then playing with a yo-yo.

Okay, onto the next line.

Ah, painting with a roller.

Then the next one is plugging in a charger.

And finally, brushing your hair.

When you've decided whether you think each of these activities involves pushes or pulls, record your ideas in a Venn diagram, which looks like this.

To make a Venn diagram, you'll need to draw two circles which overlap in the middle.

The overlap needs to be big enough to write in.

Above the left hand circle, write "push" and above the right hand circle, write "pull." Then, in the left hand circle, write the names of any of those activities you think only use pull forces.

Similarly, in the right hand circle, write the names of any of the activities you think only use pull forces.

Now, with Venn diagrams, the overlap in the middle is a very special area.

In here, you need to write any activities which you think use a push and a pull.

It's the area for things which fit into both groups.

Now it's time for you to look at those images again and make your choices about pushes and pulls.

Just like you did with the earlier questions, you might find it helpful with each one to mind the action.

That always helps me decide if I'm pushing or pulling.

Pause the video here to discuss your ideas with a partner.

When you are ready, come back and we'll look at the answers together.

So how did you get on? Your answers might have looked like this.

In the push circle, you should have moving forwards on a skateboard, because you push against the ground with your foot, and you should have plugging in a charger, because you push it in with your hand.

In the pool circle you should have brushing hair and the tug of war.

Now, what about that special middle area? Which activities use pushes and pulls? Well, when I play with a yo-yo, I flick my hand down to push and I flick it up in a pull, so a yo-yo pushes and pulls.

Now, when I paint with a roller, I can feel that I push the roller away from me and then I pull it back towards me, so that uses both pushes and pulls as well.

Let's move on to the second part of our learning today, where we're going to think about contact forces.

Some forces are contact forces.

Contact forces happen when two objects are touching each other.

Look at these cars, their bumpers are touching.

These two cars are in contact with each other.

What about these two? Are they touching? No, they're not.

These two cars are not in contact with each other.

Let's look at some more contact forces.

Why is this push a contact force? In the photo, the person is pushing the door.

Well, the person can push the door because their hand is touching it.

Their hand is in contact with the door.

How about another one? Why is this pull a contact force? In the photo, the child is pulling the toy train along on a string.

What's touching what? Ah, the child is touching the string, and the child can pull the string because their hand is touching it.

Let's think about this football moving across the floor.

When the ball rolls along the floor, there is a contact force between the ball and the floor.

This contact force is known as friction.

The force slows down the ball as it moves across the surface of the floor.

Let's see what we've learned so far by checking our understanding.

Which of the following activities does not need a lot of friction force? Is it A, skating, B, climbing a rope, or C, running? That's right, it's skating.

There's not a lot of friction needed between the ice and the ice skate, 'cause we want the skate to glide quickly.

Let's try another one.

Contact forces act between two objects that are.

each other.

What is the missing word? Ah, that's it.

Contact forces act between two objects that are touching each other.

Let's try one more.

Which of the following pictures does not show a contact force? A, pedalling a bike, B, this magnet sticking to the fridge, or C, opening a door? This one was a bit harder.

The answer is B, the magnet sticking to the fridge.

It's sticking to the fridge even though it's not touching it.

It's only touching the paper note, so this is not a contact force.

Now it's your turn again.

Think of something that you do that uses a contact force.

Are you imagining yourself doing it? Where is the contact between the objects? Is there a push or a pull? Lucas is thinking about this too.

He says, "I wonder where the contact force is when I use the zip to fasten my coat." Pause the video and think about something you do and where the contact forces are.

How did you get on? You might have thought of something like Lucas.

He said, "When I fasten my coat, my hand is touching the metal zip.

I pull the zip to fasten my coat." Was your action a push or a pull? Maybe it was one of those special activities that uses a push and a pull.

Let's move on to our final section.

We are going to look at contact forces in everyday life.

We've already worked out that contact forces are all around us.

I bet you've already thought of lots of things you do every day which involve contact forces.

What other examples could we think of? Pushing a car to move it up a hill is a contact force.

Kicking a ball to move it through the air is a contact force.

Catching a ball to stop it moving is also a contact force.

Now, we know that kicking and catching are contact forces, but are they pushes or pulls? Look at this child kicking the ball.

Imagine what you would do if you were them.

Are you pushing or pulling? That's right.

Kicking a ball is a push force.

The person is pushing the ball away from them to make it move.

What about catching? Imagine the action, perhaps mime it.

Are you pushing or pulling? That's right.

Even though it doesn't feel like pulling a piece of rope, catching a ball is a pull force.

The person is pulling the ball towards them to stop it moving.

We can use arrows to show the direction of the force.

On the left, the blue arrow shows the kicked ball being pushed away.

And on the right, the blue arrow shows the ball being pulled closer.

Let's check our understanding.

Which of these contact forces in everyday life involve pulling? A, catching a ball, B, hitting a ball with a bat, C, opening a drawer, and D, opening a packet of crisps? Remember to do your miming to help you think.

Well done.

Three of them involved pulls.

They were catching a ball, opening a drawer, and opening a bag of crisps.

The other one was a push.

Let's try another check.

Alex and Sofia are discussing contact forces in their lives.

Alex says, "All activities involving contact forces use a push or a pull but not both together." But Sophia says, "Some activities involving contact forces use pushes and pulls together." Who do you agree with and why? That's right.

Sofia is correct because some activities, like cutting wood with a saw, for example, involve pushes as well as pulls.

Now it's time for your final task.

Look at these images.

They are all activities you might have tried, and they all involve contact forces.

We have plucking a guitar string, flicking an elastic band, using scissors, walking, and opening a drawer.

You need to decide where the contact force is taking place.

You might be able to try the activities to help you to decide.

And then, on each photo, draw an arrow where the contact force is taking place.

And then label the arrow with the word push or pull to show which type of force it is.

So how did you get on? Did you find some easier than others? Your labelled photos might look like these.

Plucking a guitar string involves a pull force.

So does flicking an elastic band.

Using scissors involves push forces and so does walking.

Finally, a pull force is used to open a drawer.

Did you put your arrows in the correct place? Were they facing the right way? Well done, we've come to the end of our lesson, so let's look back over our learning from today with a summary.

A force is a push or a pull.

A push is a force that moves an object further away.

A pull is a force that moves an object closer.

Some forces are contact forces and these occur when objects are touching each other.

Pushing a cart or kicking a ball are all examples of contact forces.

We've looked at lots of other examples of contact forces and thought about some of the ways in which we use pushes and pulls in our lives.

Thank you for joining me this lesson.

It's been great fun learning about contact forces together.

Now, we've thought about so many ways in which we use contact forces every day.

I feel like we are all experts on the subject.

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

I wonder if you'll notice any pushes and pulls later in the day.

See you next time.