Lesson video

Hi everyone.

My name is Miss Hummel and I'd usually be a teacher in the school in Felton.

In this lesson, we'll be answering the question.

What are forces? We will learn what forces are.

We will also learn about contact forces and non-contact forces.

And finally, we will test our knowledge with some application questions.

Our lesson will follow this structure.

First, we will find out what are forces? Then we will learn about contact forces, followed by non-contact forces and some application questions.

In this lesson, you will need an exercise book or paper, a pencil, or a pen, a coloured pencil, or a pen, and a ruler.

If you haven't got those things, pause the video now and go get them.

These are our star words, which are most important words of the lesson.

I will go like this when I'm saying the word and I will go like this when I expect you to say it back.

Forces.

Push.

Pull.

Air resistance Water resistance.

Friction.

Upthrust.

Gravitational, and magnetic.

Now forces and push and pull are words, which are going to help us understand what forces are.

Air resistance, water resistance, friction and upthrust, all relate to contact forces.

And gravitational and magnetic relate to non-contact forces.

Now forces are a push or a pull on an object.

Now, can you remember the definition for forces? We just said it, say it out loud.

Hopefully you said that forces are a push or a pull on an object.

Now, when a force pushes or pulls on an object, it can do three things to that object.

It can speed it up or slow it down, change it's direction or change it's shape.

I wonder can you remember now? What are the three things that are force can do when it pushes or pulls on an object? The little pictures there and might help you remember.

Hopefully you were able to say all three things.

Now, I would now like you to pause the video, to complete this note-taking task.

Write down the definition of a force and write the three things it can do to an object.

You can resume, once you're finished taking those notes.

Now there are lots of types of forces which can act on an object.

Sometimes those forces only take place If two objects are touching.

We call these forces, contact forces.

Examples of contact forces include friction, air resistance and water resistance and upthrust.

Friction is a force between two surfaces that are sliding or trying to slide across each other.

Can we try and think of an action to help us remember the definition of friction? Now you could say something like friction is a force.

I'm going to say force like a fist because it's strong, between two surfaces that are sliding or trying to slide across each other.

Now let's see if you can remember the definition.

Can you say it out loud? Friction is a force between two surfaces that are sliding or trying to slide across each other.

It's important for us to know that friction always slows a moving object down.

Now, can you think of an action which would result in friction? I will give you a clue.

We've done one of those already to help us remember the definition.

You may have been thinking of rubbing our hands, just like this.

We can feel some friction when we do this.

Now friction occurs when objects move through the water or air as well.

Air resistance is a type of friction between air and another material.

Although air is something that we cannot see, air is still something.

And so it does cause contact between itself and something else.

Air resistance acts when something tries to move quickly through air.

Can you think of any objects which will move quickly through the air and will therefore be subjected to air resistance? What objects can you think of which move quickly through the air? Now you can feel air resistance when you're running fast and the air pushes your hair and your clothing backwards like you can see in the picture on the left.

You may have thought of an object that moves quickly through the air.

And you may have thought of a plane.

A plane can also feel that when it's travelling through the air.

The air particles are hitting the aeroplane, making it more difficult for it to move through the air.

You can see a picture of that on the right.

Water resistance is a type of friction between water and another material.

It's pretty much the same as air resistance, except instead of air we've got water.

Now you may notice this when you're swimming, as you can see by the diagram over there.

When you are swimming, there is a force of water pushing against you.

So we said with water resistance, you can feel it when you swim fast.

There's friction between your skin and the water particles.

And a boat can also feel this when it moves through the water, water particles hit the boat, making it more difficult for it to move through the water.

Our final contact force is upthrust.

It pushes objects upwards on objects that are in water.

You feel this when you swim, it makes you feel lighter than you would be out of the water.

And it also makes things float.

So let's not get it confused with water resistance, water resistance occurs when you're moving through the water and you're feeling the water kind of push against you.

However, upthrust is a force that is coming from below and is helping you keep a float and is helping different things keep afloat as well.

I would like you to pause the video to answer this question.

What were the four examples of contact forces? Resume once you're finished answering the question.

Now hopefully you should have written friction, air resistance, water resistance, and upthrust.

The next type of force we're going to learn about, are non-contact forces.

Now for other forces, they will act even if two objects are not touching.

We call these forces non-contact forces.

Gravitational force is a type of non-contact force.

It pulls everything downwards towards the earth.

This is the force that sticks you to the ground and makes everything else do the same.

So as a child, I used to always wonder why is it that if the earth is round, the people who are, for example in Australia are not falling? Because in my head, they were upside down and I was thinking they must be falling because I noticed that when things are upside down, they fall.

And it wasn't until I was older, that I realised that something called gravity existed, which pulls everything towards the centre of the earth, which means that no matter where you are on the earth, you're not just going to fall off into space.

And the second non-contact force that we need to know is magnetic force.

It makes magnetic objects, either attract each other, which means they pull each other together or repel each other, which means they push each other away.

I would now like you to pause the video, to answer this question.

What were the two examples of non-contact forces? You can resume the video, once you finished answering the question.

You should have written gravitational force and magnetic force.

You're now going to complete an activity to match the words that we have learned so far with their definitions.

The words that we've got on the left hand side are air resistance, gravitational force, friction, magnetic force, and upthrust.

And the definitions that we have on the right are, the first one is pushes objects upwards on objects that are in water.

The second one is pulls everything downwards towards the earth.

The third one is acts when something tries to move quickly through air.

The fourth one is acts between two surfaces that are sliding or trying to slide across each other.

And the last one is which makes magnetic objects attract or repel each other.

Pause the video to complete the task.

You can resume once you've finished.

You should have matched the following words in this way.

You should have matched air resistance with acts, when something tries to move quickly through air.

Gravitational force with pulls everything downwards towards the earth.

Friction with acts between two surfaces that are sliding or trying to slide across each other.

Magnetic force with makes magnetic objects attract or repel each other and upthrust with pushes objects upwards on objects that are in water.

Hopefully you got them all right.

But if you didn't, remember that, that's an opportunity to learn from your mistakes.

For the final part of our lesson, we're going to think like scientists and interpret and present some data.

We will also just be completing some application questions which are going to help us understand forces.

First, we're going to complete an activity where you need to identify which force is shown in the diagrams. In our first image, we have a picture of a man with an apple on top of his head and some arrows pointing down.

in the second picture, we have a rubber with two arrows going in opposite directions.

And in our final diagram, we have a boat with an arrow pointing the opposite direction in which it's going.

I want you now to write which force is being shown in which diagram? Pause the video to complete the task.

Hopefully you wrote that the man with an apple on top of his head was experiencing gravitational force.

The rubber was friction and the boat was water resistance.

Now we have two more diagrams for you to identify which forces are being represented? In the first diagram, we have one dog sticking it's head out of a window with arrows pointing towards it.

Then we have a diagram of a magnet with some metal nails stuck to it.

Not nails like these, but nails like what you would use to build some furniture.

Pause the video and complete those two questions.

Hopefully you wrote that the dog was air resistance and the magnet picture was magnetic force.

In this next activity, you'll be faced with some different scenarios, which are what has happened.

Then you will need to write what force has acted in that scenario? And finally, you will need to write why you think it was that force? And you should present it as a table like you can see on the screen.

The first scenario is Jennifer fell over and scraped the skin on her knee.

Which force acted on her skin? This question is an example, and it's already been completed.

It tells us that friction acted because the force was caused by the floor and her knee rubbing against each other.

The second one is, when Julia's ball fell into a pond, she noticed it did not sink.

Which force pushes upwards from the water? The third one says, Maryam placed a new fridge magnet onto the side of the fridge.

And it stayed stuck to the side, which force keeps it sticking to the fridge? And the last one says, Thomas has toy soldiers, and he noticed that the one with a parachute falls slowly to the ground when he drops them from the top of the stairs, when the others fall quickly.

Which force is slowing it down? So you now have three questions to complete in this table.

We'd like you to pause the video so that you can complete this task.

Now, hopefully you wrote that for Julius scenario, It was upthrust that was acting on the ball because it meant that the ball did not sink and was pushed up from the water.

Maryam's was magnetic force because the magnet was being used, and Thomas was air resistance because the parachute had greater air resistance due to its size than the toy soldiers without it.

For our final activity, I would now like you to pause the video, to answer this question.

What are all the forces which are acting on a boat when it's moving forwards in water? You may think of one force, but there's more than one.

Resume the video once you finished answering the question.

Now you should have written gravitational force because gravity's acting on everything that's on earth.

Upthrust, which is keeping it floating in the water.

Water resistance, when it's moving, it's going in the opposite direction, and some air resistance, because half of the boat wouldn't be in the water, Half of the boat is getting some air resistance while it's moving as well.

So in that one scenario, we had lots and lots of forces acting on that object at any one time.

And that's the case for most things in our world as well.

It's not usually just one force that's acting on it, It's actually quite a lot.

I'm sitting right here, but yeah, I've got quite a few forces that are acting on me, like gravity.

Now we have finished our lesson and it is time for you to complete your exit quiz.

You need to exit the video and complete the quiz to test your knowledge and understanding of this lesson.

I really hope you enjoyed the lesson as much as I did.

Bye.