Hi there, I'm Mrs. Kemp, and welcome to today's lesson all about biomechanics.

This fits into the human skeleton and muscles unit.

So some of the content will be familiar to you.

You might also recognise some of it from the human skeleton topic back in primary.

There is some new words and some new information, but don't worry, I'll be here to help you.

I'm so pleased that you have decided to learn with me today.

So let's get started.

Okay, so our outcome for today is I can calculate the moment of a force around a joint.

Now, because we're gonna be doing some calculations, you may wish to grab yourself a calculator.

Please pause the video now if you wish to.

Otherwise, our key words for today are biomechanics, muscle contraction, force, moment, and pivot.

Now, I will be going through each one of these words as we go through the lesson, but if you'd like to pause the video and have a read of them now, please do that.

So we have two learning cycles for our lesson on biomechanics.

The first learning cycle is biomechanics itself and the second one is how to calculate moments.

All right, so we will be starting with biomechanics.

Okay, so we're gonna start by watching a video.

This video is a clip of a boy kicking a ball.

Now, whilst video is on, what I'd really like you to do is think about how his body is able to do that.

What's involved in moving his body and how does that move? Okay, so we're gonna have a watch.

I would let you have a think.

(ball thumping) If you need a little bit more time to think about that, do pause the video.

So actually how his body moved is biomechanics, okay? The movement of all of the different parts of his body that are involved in that contribute to the full movement, that biomechanics.

It involves muscles, okay? Bones, tendons, and ligaments.

And they all need to work together in order to help them move.

So when a basketball player there, he's spinning that ball on his finger, all right? When he is gotta bounce that ball, there's gonna be movement of those different parts.

You can see the runners on the right hand side as they're moving, all right, all of those parts of the body are going to be working together.

There is a great deal of movement of all the different type of muscles pulling all the different types of bones through tendons, and of course those ligaments that are holding those bones together.

Okay, let's really break that word down then so that we can understand it.

The word starting with bio, whenever we have a word that starts with bio, it means it's related to living things.

So, for example, biology, all right, is the study of living things, okay? Mechanics on the end of that word is related to studying the working parts of something and how they move.

Now, because it's got bio on the front of it, those working parts are within a living thing.

Another word that has mechanics on the end of it is hydromechanics, and that is the study of the movement of water, okay? So bio meaning life, mechanics meaning the study of working parts, so biomechanics is the study of working parts in living things.

Let's go on to our first check then.

So, what is biomechanics? Is it A, the study of how all things move? B, the study of how living things move.

C, the study of living things, or D, the study of movement? I'll give you a short amount of time to think about that, but if you do need more time, please do pause the video.

Excellent.

Did you put B? Great, biomechanics of course is the study of living things and how they move.

So, who is actually interested in biomechanics? Biomechanics is used in all types of sport in order to improve their performance, okay? So there are actually lots of people that are studying biomechanics and then passing on that information to our athletes to help them to improve.

You can see that we've got some people in a steeple chase there and we've also got a young child kicking a football.

Scientists would want to look at the interaction between the skeleton and the muscles and measure the force exerted by those different muscles and the energy required to move so that they can best advise their sports people to improve on their particular chosen sport.

So it might be that they want to tell them about diet and how they can improve their diet.

It might be that they want to show them a better way of kicking that football in order to get the most force behind it and power it through the air.

Okay, remember back in the earlier topic that actually, we have muscles that work together in pairs.

Those pairs are known as antagonistic pairs of muscles and what they do is they're able to exert a force on the bone, all right, by pulling on the tendons that then pull on the bone.

We're going to look at an arm as an example and how we're able to move our forearm up and down.

Now let's take a little closer look inside that arm.

All right, inside the arm we've got a bicep in here.

Our biceps are the ones that are on the top of our arm, and we've also got our triceps that are on the bottom of the arm here.

And the tendons, remember, attach our muscle to the bone.

The the muscle does not attach directly to that bone.

So when our biceps contract, they pull on the tendons that pulls on the bone in our forearm, all right? And remember that when one of our antagonistic muscles contracts, the other one will relax.

So which of these are an antagonistic pair of muscles? Is it a, bones and joints? Is it b, biceps and triceps? Is it c, triceps and bones? I'll give you a little moment to think about it, but if you do need more time, please do pause the video.

Did you think it was b, biceps and triceps? Brilliant, well done.

All right, we're going to have a little go at making a model together.

For this model, you will need some household materials.

So we've got two lollipop sticks here.

I've got two very small bands, elastic bands, and then I've got two larger bands.

The tiny elastic bands are just there so that we can hold our lollipop stick into the shape of our arm, okay? So this is the first thing that I'm going to do and you just need to loop those elastic bands around the lollipop.

Okay, so my lollipop sticks now look like this.

To make it a little bit easier for myself, I've already cut myself four pieces of sticky tape, okay? So I do recommend doing that for the next stage.

So what we're going to do is we are now going to make our biceps and our triceps, so our antagonistic pair of muscles.

I will make my bicep first by wrapping it around the top lollipop stick like this and then around my second lollipop stick like this, and I secure it in place with that sticky tape like so.

I then need to make my triceps, so I get my second big elastic band and I put that looping onto the same place and I put it in place with my sticky tape like so.

And then I need to bring it back around the bottom part and again, secure it into place.

It helps if you then pull those elastic bands and just secure those around the bottom of the lollipop stick like this.

It is a little bit fiddly, as you can see, but you should have something that looks a little bit like this in the end.

You can see that we've got our biceps on the top and our triceps behind.

Think about where they are on your arm, our biceps on the top, and our triceps underneath, and we've got that shape, haven't we, of our arm.

Okay, so let's use this model now to go into our first task.

So using our biomechanical model of the triceps and the biceps, number one, hold one of the bones.

So the lollipop sticks are our bones, aren't they? All right.

And try pulling on those elastic bands and see what happens.

Then discuss with your partner, or if you are on your own, have a little think about it to yourself.

How is this model a good model of how the elbow joint works and how can it be improved? Now, I'll give you a little bit of time to do this, however, if you haven't made your model, you're going to need a little bit more time.

So please do pause the video in order to do that.

Otherwise, if you've already got it ready, you can have a little think about those questions.

Off you go.

Okay, so when you pulled on your elastic bands and holding onto one of them, you should have noticed that as they contract and get shorter, it will move that bone.

Okay, we can pull on our triceps and they will move that bone back down again.

So let's have a look at what Aisha thought then as a positive for our model.

So Aisha thinks it's a good model because it shows that the joints can only be moved by muscles pulling on the bone.

Good, Aisha, well done.

However, and Jun is right here, it doesn't show all the muscles in the arm, okay? It's only showing the biceps and the triceps, and it shows the muscles actually being directly attached to the bone.

And we know that that's not correct, don't we? We know that actually there are tendons in there that are attaching that muscle to the bone.

Okay, brilliant.

I hope you thought of those.

You may have thought of some other ones, because it's definitely not a perfect model, but I'd like you to keep hold of it 'cause we do need it again.

All right, let's go into our second learning cycle, which is calculating moments.

So again, you may need a calculator for this section.

So when the force of a muscle moves the bone, it actually causes a turning effect.

You can see that as my arm is moving, it's moving in a circular motion.

This is called a moment, all right? So as it's moving around like this, it's causing a moment, and this is because the muscle inside there is contracting and this will pull on the bone.

Let's have a look at another type of moment now, where a moment is acting from a force.

This is a wrench that is turning a bolt on a radiator.

The forces that create a moment then act around a pivot.

Now, in this example of the bolt, this is the pivot, and the pivot is the point at which the object can rotate, so turn.

The force exerted by the hand that is pushing that wrench down, okay? Causes the circular movement around the bolt, or the pivot as we know it is.

Think about your arm moving around a point, it's moving around the point of your elbow, isn't it? And that would be the pivot.

Now, we can actually calculate the moment on our joints using an equation.

The moment is equal to the force times the distance.

Now, the moment has the units of Newton metres, the force has a unit of Newtons, and the distance has a unit of metres.

Now, you can see here that actually Newton has a capital N, so don't miss that out when you are doing your calculations, and distance has a lowercase m.

So we'll look out for that when we're doing our calculations as well.

The lady in the picture is holding a mass in her hand, okay? This is creating the force and the distance is the point from the pivot to that force.

It's from her elbow, remember, which is the pivot in the arm, and the force is where she's holding it in her hand.

So there's our pivot at our elbow.

Now, let's try using that calculation then.

So if a woman lifts a mass of one kilogramme, now, one kilogramme is equal to 10 newtons.

So if we want to use it in a calculation, then we must first of all calculate a kilogramme into a Newton, okay? What is the moment about her elbow if the distance from her elbow to the mass is actually 0.

3 metres? Again, we've measured in metres that's very important.

So let's put those numbers into our calculation together and we'll do this one in real time.

So 10, remember, is our mass, so that's our force, and we times that by the distance, which is 0.

3.

So actually, our moment is equal to three Newton metres.

Again, look again, we've got Newton in capitals and metres in lowercase.

Okay, you are going to have a go at this yourself.

Please use calculator if you like, but you may be able to do it in your head.

So, this is our first check in this learning cycle.

A woman holds a five kilogramme, which is 50 Newtons, bag of sugar in her hand.

The distance from her elbow to the sugar is 0.

35 metres.

Can you calculate the moment around her elbow? So the moment, remember, is force times distance.

I will give you a moment to think about it, or a little bit of time I should've said really, to think about that.

But if you need more time, please do pause the video.

Okay, so if we use 50 newtons as our force and we use 0.

35 metres as our distance, then we have 50 times 0.

35, and that gives us a moment of 17.

5 newton metres.

I hope you got that right, otherwise you might need to go back and check your calculations again.

So we're onto our final task of today, and please do use your worksheet to help you as you need to label something from your model.

So grab your model back that we did in learning cycle one of our forearm with our biceps and our triceps.

So the first thing that you need to do is locate the position of the pivot and label it with a P.

Now, actually, it would probably be easier to label it on your worksheet, but if you need to, if you've got a lollipop stick, you can actually write on lollipop stick.

So it'd be fine to write it on there.

You also need to measure the distance between the pivot and the position of where the hand would be.

So you will need a ruler for this, but remember, you need to convert whatever you've measured into metres.

Number three, then calculate the moment required for your model arm to lift the following weights, 10 Newtons, b, 45 Newtons, and c, 3.

56 newtons.

All right, so you will need that equation from earlier and you'll need to substitute the numbers that you have measured and then also that are in that question.

I will give you a little bit of time to think about it, but please do pause the video if you need a little bit more time.

Okay, so did you realise that the pivot, of course, where our elbow is, is this point here where we've got those tiny elastic bands.

If you labelled it on your diagram on the worksheet, or if you actually labelled it on your lollipop stick, that's fine.

When I measured the distance between the pivot and the end of the position of the hand, I got naught 0.

1 metres.

However, you may have got a slightly different number for that.

As long as you put it into the calculation in the same way, then it's absolutely fine.

So number three, if I use 0.

1 metres for my distance, then for a, I get my force times my distance, 10 times 0.

1 is equal to one Newton metres.

For b, I get my force times my distance, I get 45 times 0.

1 gives me 4.

5 Newton metres.

And then finally, for c, I get 3.

56 times by 0.

1, which is equal to 0.

356 Newton metres.

If you measured your distance slightly different to mine, you may have slightly different answers.

However, the technique should be the same.

All right, so we finished our learning cycles for today and our final task, and now we're moving on to our summary.

So biomechanics is the study of how the body moves.

Biomechanics is used by athletes to improve their performance.

Muscles attaches to bone with tendons and exerts a force on the bone to make it move.

Muscles move bone around joints, which can act as pivots, causing a turning effect known as a moment.

We can calculate a moment using the equation moment is equal to force times the distance.

Thank you so much for being in the lesson with me today.

I've really, really enjoyed it.

I hope you have too and I look forward to seeing you again sometime.

Thanks very much.

Bye now.