Hi everyone, it's lovely to be learning science with you today.

I'm Dr.

Pemberton, and I'm really looking forward to working through the lessons with you, so let's get going.

Today's lesson is called, How pulleys can help us.

I wonder if you can think of somewhere that you have seen a pulley.

The learning outcome for today is that you can describe how pulleys can make difficult work easier.

It's part of our big question, how do forces make things happen? I'm looking forward to working as a scientist with you to learn more about this, I hope you are too.

These are the key words that we'll be using in today's lesson, pull, pulley, load, effort, and force.

Some of these words are new today, but some of them should be familiar to you already.

This slide shows the meaning of each of the keywords.

I'll explain these words as we come across each of 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're confident using each one of those words.

This is our lesson outline for today.

There are three parts to the lesson.

We'll begin by learning how pulleys can help us, then we'll be investigating pulleys, and finally, we'll learn how pulleys are everywhere.

We're gonna get going on the first part of our lesson now, pulleys can help us.

Have you ever seen a window blind like this? The rectangular fabric part is the blind and there's also a plastic chain at the side.

If you wanted to get more light in, how would you lift the blind to open it? To open the blind, you pull down on the chain and the blind moves upwards.

It works with a pulley system.

A pulley is a mechanism or simple machine, which is useful for lifting things.

A mechanism or machine does not have to be complicated like an engine or a robot.

It's anything that has moving parts which move together to help us to do work more easily.

Pulleys and levers are both simple machines.

Ah, here's Sofia, and she says, "I wonder what a pulley looks like, do you know?" A pulley often consists of a wheel with a groove, through which rope or chain runs.

Here we can see a diagram showing the grooved wheel, and there's a red rope threaded up and over that wheel, and then back down the other side.

The rope has the load on one end and someone or something pulling the other.

You can see the load on the picture attached to one end of the rope, and you can also see the direction that someone pulls down to lift the load.

The pull is called the effort, and this is the force applied to lift the load.

There are different ways that pulleys make it easier to lift things.

Some pulleys make it easier because they change the direction of the force needed to lift an object.

You can see that on this diagram, the hand is pulling downwards, but the load is moving upwards.

So the direction of the effort is down and the direction of the movement of the load is up, just like the arrows show, and it says, with this pulley, you pull down to lift the load up, just like with the window blind.

So with the window blind, I'd pull the plastic chain down and the rectangular fabric blind would move upwards.

Let's check what we've learned with a couple of questions.

This one's a multiple choice question, it says, pulleys and levers are examples of simple blank, which are useful for lifting things.

Should the blank be replaced with A, motors, B, machines, or C, engines? Well done if you chose B, machines.

So the full sentence should be, pulleys and levers are examples of simple machines, which are useful for lifting things.

Let's try another one.

Look at the diagram of the pulley.

Do you know the different parts? Which part is the arrow pointing to? Is it A, the rope, B, the grooved wheel, C, the load, or D, the effort? That's right, it's B, the grooved wheel.

Okay, we've got another one.

So the same diagram, but this time the arrow is pointing at a different bit.

Is the arrow pointing at A, the rope, B, the grooved wheel, C, the load, or D, the effort? That's right, it's C, the load.

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

This is your first science challenge for the day.

You are going to try some activities to help you explore how pulleys make it easier to lift a load.

You're going to use a recycled plastic milk bottle as your load.

You'll need to fill it with water to make it heavy enough.

You'll also need a bit of string to tie to the handle, and that string will need to be about two metres long.

Your first task is to tie the string to the bottle and use it to lift the load into the air.

Try to notice how heavy it feels, is it difficult? For the second part of the task, you'll need to lift the load using a simple pulley made from a broom handle balanced over two chairs.

Stand the bottle on the floor under the broom handle, then thread the rope over the top of the broom.

Now pull down on the rope to lift the bottle off the floor.

You might need to sit on the floor to make sure that you are low enough to do this.

How difficult is it each time to lift that load? It is time for you to pause the video and try the tasks.

When you finish, come back and rejoin me for the next part of the lesson.

Welcome back, how did you get on with your task and what did you find? You might have found something like this.

This person said, "It felt easier, less effort, to lift the carton, the load, by using the pulley and pulling down on the string than it was to lift it just by pulling up on the string." It's interesting, did you find that? Now, we're going to move on to the second section of our lesson and we're going to be doing a bit more work on investigating pulleys.

This diagram shows a different type of pulley, let's have a look.

It still has a grooved wheel, but this time the wheel isn't attached to the ceiling.

Instead, the rope is attached to the ceiling and then the rope comes down from the ceiling to thread through the wheel.

Can you notice how with this pulley, the load is attached directly to the pulley wheel, whereas before it was attached to the rope? The wheel and the rope are arranged so that you pull up to lift the load.

You can see the hand ready to pull up.

This means that the effort is in the same direction as the movement of the load.

This type of pulley works by decreasing the effort force needed.

You can see arrows on the diagram to show that the direction of the effort is the same as the direction of the load, they both go upwards.

Because less effort or force is needed to lift the load, it's easier to lift.

Pulleys, which reduce effort, help people to lift really heavy objects in the construction or building industry.

Here you can see a crane with a pulley, which is used to lift really heavy objects.

Starting from the top label, you can see the chain, and this one's big and thick and made of metal, unlike the one for the window blind that was thin and made of plastic.

Then coming down you've got the pulley wheel, and finally, a hook to attach to the load.

Some pulley systems have lots of wheels.

In this picture, you can see a pulley with three wheels, each has got a rope threaded through it.

These pulley systems with lots of wheels can change the direction of the force and reduce the effort of the force needed to lift an object.

Let's see what you can remember with a couple of questions.

Laura and Sofia are talking about pulleys.

Who do you agree with? Laura says, "Pulleys help us because it changes the direction of the force needed to lift the load." Sofia said, "A pulley helps us because it reduces the effort needed to lift the load.

Laura and Sofia are both correct, you can change the direction needed to lift it, and that can make it easier, and you can change the effort, and that can obviously make it easier.

Let's try another one.

Look at this diagram of a pulley.

Is the effort in the same direction or the opposite direction to the movement of the load? Do you think it's A, same direction, or B, opposite direction? That's right, it's A, the same direction.

The effort is a pull upwards and that makes the load move upwards.

Now look at this pulley and think about the same question.

Is the effort the same direction or the opposite direction to the movement of the load? Do you think it's A, same direction, or B, opposite direction? This time it's B, the opposite direction.

The pull is downwards and the load moves upwards.

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

Here's Laura, she says, "We are going to compare the force needed to lift an object with and without a pulley.

Make a prediction, do you think it will be easier to lift the bottle with or without the pulley, and why?" Okay, have you got an idea? Let me show you what you need to do.

You are going to explore how pulleys can make it easier to lift a load.

You'll need to get the same equipment that you used in task A, but you'll also need a force metre and a movable pulley.

Do you want to go and get those now? First, you are going to measure the force needed to lift the milk bottle without the pulley.

So you'd hook the metre directly into the bottle and lift it off the ground, and then read the value on the force metre to see how much effort that's taking.

Then in the second part of the task, you try lifting with the pulley.

This time you're going to use the second type of pulley, just like shown in the photo here.

The pulley here, which is the red circle at the bottom, is tied directly to the handle of the milk bottle.

In a minute, you're going to see a video of this.

You'll tie the string to the broom handle, and then you thread the string that you've brought downwards through the pulley.

Next, you need to tie a knot into the string and hook the force metre into the knot.

Now, gently pull up on the force metre to lift the bottle off the ground.

Measure and record how many newtons this takes.

Pause the video now and go and try the experiment and then come back and join me.

How did you get on? What did you find? Was it something like my results? So remember, you were exploring how pulleys make it easier to lift a load, and your results might have looked like this.

I've put my results in a table so they're easy to follow.

It took 14 newtons to lift the load directly, but when I used the pulley, it only took seven newtons.

The pulley reduced the effort needed to lift the carton.

It took nearly twice as much effort to lift it without the pulley as it did with the pulley.

Wow, so that pulley really made the job easier for me, it halved my effort, did you find the same? We've come to the final part of our learning now, we're going to see that pulleys are everywhere.

Pulleys are used in many places in everyday life.

Sometimes pulleys are used to lift something from or to a place that's hard to reach, so they're not only used to make it easier to lift heavy things, but sometimes they're needed because we are lifting things to or from awkward places.

What's the load being lifted with a pulley in each of these photographs? What do you think? Let's start on the left.

We've got flags being lifted up a flagpole, so the reason the pulley helps here is because the flag is going up really high, somewhere we couldn't reach.

In the middle, we've got a bucket lifted up from a well, so that's lifting something from a place that's really difficult to reach.

And finally, we've got a drying rack, so this is where you'd hang clothes to dry them in the house, and this is lifting them up and away so they won't get dirty or get knocked by people.

Often, we can't see the pulleys that are in use because they're hidden.

What everyday objects are using pulleys in these pictures? Starting on the left, there's a picture of some lifts or elevators which use pulleys.

Then in the middle, we have a red garage door, they've got pulley hidden inside to make it easier because the door's really heavy.

And then finally, we've got a cable car, and they use pulleys to move them along in and out of the mountains.

Pulleys can also help people exercise by making it safer to move really heavy weights.

Pulleys can help sailors raise their really heavy sails up high to the top of the mast.

Pulleys are also used in construction and building to lift and move heavy objects.

On the left, you can see builders attaching a pulley to a heavy piece of equipment, and on the right you can see cranes used also in construction for moving heavy stuff really high up.

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

Which of these involves a pulley? Is it moving washing on a line or moving a heavy load with a wheelbarrow? That's right, it's moving washing on the line.

The line is threaded through a pulley at the top of the post, so you can lift the line and move the clothing up high and out of the way.

Let's try another one.

This one's a multiple choice question.

Which of the following are reasons that people use pulleys? Is it A, they can reduce the mass of the thing you were lifting, B, they can reduce the effort needed to lift heavy things, or C, they can make it easier to lift things from places that are difficult to reach? That's right, it's B and C.

Pulleys can reduce the effort needed to lift heavy things and they can make it easier to lift things from and to places that are difficult to reach.

Now it's time for your final task.

Jun, Alex, and Izzy have taken photographs of pulleys in everyday life.

On the left, they've got the window blind that we looked at before, and on the right they've got the washing line with the pulley that was in the previous photo.

You need to choose one of these photos and label the wheel, the load, and the effort, so you'll need to put some arrows on it for those.

It is time for you to go and do the task now, come and join me when you've tried it.

How did you get on? I labelled the window blinds, and you can see that I've labelled the wheel, the effort pulling the chain down, and the load, which is the blind itself moving upwards.

Your photo might look like this or you might have done it slightly differently.

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

A pulley is a mechanism or simple machine which is useful for lifting things.

A pulley often consists of a wheel with a groove, through which rope or chain runs.

The object you are lifting is called the load, the force you apply to make an object move is called the effort.

Some pulleys make it easier because they change the direction of the force needed to lift an object.

Some pulleys make it easier to lift an object because they decrease the effort needed.

Well, thank you for joining me.

It's been great fun learning about pulleys together in this lesson, and I wonder if it's made you think of any pulleys in your life.

Perhaps you've seen one at home or in your town, try and look out for them and notice them when you see them.

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

I'll see you next time.