Lesson video

Hello, welcome to this lesson called Reducing Friction Analysis.

My name's Mr Norris.

In this lesson we're gonna be looking at how you can analyse and draw conclusions from scientific data to do with an experiment into friction and lubricants which reduce friction.

The outcome of this lesson should be that you'll be able to analyse data from an investigation to test the effectiveness of different lubricants.

Here are some key words that will come up this lesson.

Lubricant, friction, categoric, continuous, and conclusion.

Each word will be introduced at the appropriate point in the lesson as it comes up.

The lesson is split into three sections.

The first section looks at some results from an experiment into friction and lubricants and looks at how we can present those results in a graph and how to do that.

The second section looks at how we can then draw a conclusion from those results.

And the third section looks at how those results could potentially be applied to a real-life situation.

Let's get going with the first section.

So a lubricant is a substance added between two surfaces to reduce friction.

So, for example, oils, greases, and polishes are examples of lubricants.

The oil on a bike chain or the oil that you might put on the hinge of a door are examples of lubricants to reduce friction and get nice smooth movement.

So here's Izzy.

Izzy tested the distance travelled by a mass sliding over a desk.

Izzy used three different lubricants, cooking oil, washing-up liquid, and water.

So here is a quick kind of visual reminder of that experiment.

Cooking oil and mass flicked over cooking oil, then washing-up liquid, and then the mass flicked in the same way over washing-up liquid and then water, and then the mass flicked in the same way over water.

So the elastic band was used to give each mass the same speed every time, so that the only thing that was different in different tests was the lubricant used and that might have affected the distance travelled by the mass each time and that's what Izzy recorded each time.

So let's have a look and see if that was the case.

So here are Izzy's results.

You can see the three lubricants, cooking oil, washing-up liquid, and water.

There's a couple of anomalous results which have been crossed out because they don't fit the pattern of the other results so they're treated as mistakes.

And then the means calculated from the good results.

And Izzy wants to know whether she should present her results using a line graph or a bar chart so it's gonna be our job, firstly, to help her decide.

So let's make sure we know the difference between the two.

So which is a bar chart and which is a line graph? I'll give you five seconds now to decide.

We've got graph A on the left and graph B on the right.

Which is a bar chart and which is a line graph? Five seconds now to make sure that you know.

Okay, I think you probably should have got that A is, of course, a bar chart because it's got the bars of different heights, showing the distance travelled by the different shapes of mass, which somebody might have tested doing a similar experiment.

And then graph B is, of course, the line graph.

This person's done a different experiment so they've drawn a different graph.

It looks like this person has tested a 50 gramme mass, 100 gramme mass, 150 gramme mass, a 200 gramme mass, and a 250 gramme mass and flicked each one with an elastic band in the same way and measured the distance travelled by each one.

So these students with these graphs have done a different experiment to Izzy.

So which type of graph should Izzy draw, a bar chart or a line graph? Well, let's look at how we can decide.

So, in an experiment, the things that can change are called variables.

They can vary, they're able to vary, they're variables.

So some variables, some things that can change in an experiment.

Some variables come in distinct and separate types like shape.

You can have a circle or a triangle or a square but there's no like, there's nothing in between a circle and a triangle, for example.

Each shape is just a distinct separate shape.

And that's the same with, for example, type of tree, an oak tree, an ash tree, a pine tree, a palm tree.

They're totally distinct and separate.

So type of tree and shape, they're these kind of variables that come in these distinct separate types.

Fuel is another one.

There's diesel, there's petrol, there's gas, there's fuel oil, there are different fuels.

Completely distinct, separate different fuels.

So these kind of variables, these things that you could change 'cause you could change the shape or you could change the type of tree you're testing or you could change the fuel you're using in an experiment, those type of variables, those types of things you can change, variables, they're called categoric variables because they come in different categories with no like in-between values.

But, of course, other variables, other things that can change, they have numerical values so they come in numbers on a continuous scale and all values are possible, including decimals.

You could have 9 or 9.

5 or 9.

8 or 9.

9, or 9.

98 or 9.

99 or 9.

999.

All of those decimals are possible on a continuous scale.

That's what continuous means, that's a continuous series of numbers that height could possibly take.

And same with temperature and same with volume.

So you can see continuous scale of numbers for these kind of variables.

So a very different kind of variable.

These are called continuous variables.

They're very different to categoric variables.

So let's check we've understood the difference between categoric and continuous variables.

I've got five different variables here.

For each one please just decide is it categoric, does it come in distinct separate categories, or is it continuous? Can it take any value on a scale of numbers? So I'm gonna give you about five seconds or so to decide for each of these five variables, is it categoric or is it continuous? Right, I'll go through each one.

Pause the video now if you need a bit more time.

So the first one was a type of metal such as iron, copper, zinc, or tin.

There's no in-between values.

That is a categoric variable, type of metal is a categoric variable because there's just distinct separate metals that you can test.

The amount of force measured in Newtons, that's a continuous variable because you can have any number of Newtons on a continuous scale of numbers.

So it's a continuous variable.

The same for mass.

Something's mass in grammes could be zero grammes, 0.

1 to 0.

5 to 0.

75 to 0.

8965 on a continuous scale of numbers in grammes.

Kind of mammal, humans, rabbits, dogs, cats, blue whales, dolphins are all mammals but they are all separate distinct categories.

So that's a categoric variable.

And type of lubricant is also a categoric variable because you can either use cooking oil as a lubricant or water as a lubricant, or washing-up liquid as a lubricant for example.

So they are completely separate lubricants so it is a categoric variable.

Well done if you got most of those right.

So we're now ready to explain when you draw a bar chart and when you draw a line graph.

So bar charts are used when the variable you changed in an experiment is categoric.

If you changed what you changed to a completely separate category or thing.

So in this experiment it looks like a person has changed what shape they were sliding over a surface, what shape of mass they were sliding over the surface and they measured the distance travelled every time, but the thing they changed was the shape.

So that's what they changed and that is categoric so it comes in completely separate categories.

So you need a bar for each category showing the distance travelled by each completely separate shape.

Whereas you use a line graph when the variable you changed is continuous.

So if a person instead had changed the mass of the object that was sliding across the surface, then they could have chosen any mass they wanted over a continuous scale of numbers.

So if that variable that you change goes across a continuous scale of numbers, then you need a line graph to show that data.

So you use bar charts when the variable you changed is categoric and line graphs when the variable you changed is continuous.

So should Izzy draw a bar chart or a line graph? Decide in your heads now and remember to look at what variable did Izzy change.

Is it categoric? So draw a bar chart.

Or is it continuous? So draw a line graph.

Five seconds to make your final decision on what type of graph Izzy should choose.

Okay, let's have a look.

Well done if you said Izzy should draw a bar chart.

What's the reason? It's because type of lubricant is a, which kind of variable is it? Five seconds to make sure you can fill in that gap.

Okay, Izzy should draw a bar chart because type of lubricant, the thing she changed in each test, is a categoric variable.

And when the thing you change is categoric, you draw a bar chart.

You need a bar for each category, for each distinct category that you tested.

Okay, so I would like you now to draw a bar chart of Izzy's results.

We've gone through why it's a bar chart and now I want you to just draw it.

You only need to plot the mean results, I've not included Izzy's trial one, trial two, trial three, just the mean.

So you only need to plot those mean results in the table there.

So have a go now at drawing a bar chart of those results.

You'll need a sharp pencil, a ruler, and some proper graph paper.

If you've got the worksheet that goes with this lesson, there is graph paper on it which you can just draw your graph straight on.

You should pause the video now, collect the equipment that you need, and then draw that bar chart really carefully.

Off you go.

I'm going to go through some feedback now on the graph so make sure you have finished it.

Pause the video and finish your graph first if not.

So the first thing your graph should have is axis titles, titles for each axis, including the units.

So the X axis should be labelled type of lubricant and the Y axis should be labelled the mean distance travelled, and that's in centimetres.

So that is your axis titles and the units.

Type of lubricant doesn't have units but the mean distance travelled is in centimetres.

They should be the right way round.

Then you should have done a Y axis scale.

Now, the biggest distance is 53 centimetres but the scale, it's like the scale on a ruler, it should go up in nice even steady amounts.

Makes sense to go up in tens, 10, 20, 30, 40, 50, 60.

That gives you plenty of space to go up to the biggest distance travelled which is 53, easily fits on that scale.

That's the Y axis scale.

Then a bar should be drawn with a ruler to the correct height and they should have gaps in between 'cause it's a categoric variable, which are completely distinct.

Okay, cooking oil, the bar should be exactly 53 centimetres on the scale.

So find the 50 and go up three little boxes and it should be a height of 53.

And you don't need that dash line, that was just to show you that it's exactly a height of 53.

The bar for washing-up liquid should be exactly at 14.

Now that's helpfully on one of those thicker lines.

So there's the line for 40 and that's where the bar should go up to exactly.

And then the bar for water should go up to 33.

So find the line for 30 and go up three little boxes to get you 33 on this scale.

There it is.

So three little boxes up from 30 gets you to 33 and that gets that bar to exactly the right height.

It should be 33 centimetres for water.

So that's the bars drawn with the ruler to the correct height with gaps in between.

And then the final thing you should have done is you should have labelled each bar with which lubricant that bar represents.

So we've got cooking oil, washing-up liquid, and water all labelled correctly and hopefully your graph looked very, very similar to that.

Well done if it did.

So that completes the first section of the lesson on how to represent results from an investigation on friction.

We'll now look at how to draw a conclusion.

So what is a conclusion? Well, a conclusion is the bit of an experiment writeup that states what you found out and how you know this.

So a good way of starting a conclusion is I found out that and then you say what you found out.

So in Izzy's experiment, the sliding masses slow down and stop because a friction force acts from the bench top.

So have a look at the animation, why does it slow down and stop? Because there's a friction force acting backwards on the mass.

So that's represented in the diagram there.

However, an effective lubricant would reduce that friction force.

Maybe friction was perhaps only that big now instead.

That means the mass will travel further before stopping with a better lubricant because a better lubricant will reduce the friction more, so the friction will be smaller if it's reduced more.

Let's do a quick check of that.

What do Izzy's results therefore show? Which was the best lubricant and why? Five seconds to fill in those blanks in the bullet point.

Okay, Izzy's results show that cooking oil was the best lubricant.

And why is that? It's 'cause the mass travelled the greatest distance and if the mass travelled the greatest distance, that must be because friction was smaller, it was cooking oil must have been a more effective lubricant to allow the mass to slide to the greatest distance.

So which was the worst lubricant? You should be able to fill in those blanks as well.

Five seconds, off you go.

So if cooking oil was the best lubricant, it must have been water in this experiment was the worst lubricant because the mass travelled the shortest distance.

So water reduced friction the least.

So friction stayed the highest with water.

Whereas cooking oil reduced the friction right down so the mass could travel further.

Let's do another check of that.

Draw lines to make the correct links to the best lubricant and the worst lubricant.

Five seconds to have a go at that.

Off you go.

Okay, I'm gonna go through feedback on that task now, pause the video if you need a little more time.

So with the best lubricant, that is gonna mean the mass travelled the furthest because friction was smaller.

The best lubricant is gonna reduce friction the most so friction is smallest and that's gonna let the mass travel the furthest.

And with the worst lubricant, it's just the opposite.

With the worst lubricant, the mass is gonna travel the least far because friction is greater.

The worst lubricant won't reduce friction as much so friction remains high.

So friction will be greater, the mass won't travel as far with the worst lubricant.

Well done if you got those.

So that was a very quick little learning cycle.

You should now apply what you've learned to Sofia's data.

So Sofia did the same experiment but she tested three lubricants that were on sale in a shop.

So she's put their brand names in the table.

There's one lubricant called Easy-glide, there's one lubricant called Swish, there's one lubricant called Smooth and the mean distance travelled is shown in Sofia's table.

So write a conclusion for Sofia's results.

You can use those sentence starters.

You should pause the video now and have a good go at that task.

Off you go.

Okay, I'm gonna go through some feedback now on that task.

So if you've not finished, you should pause the video and finish your task first.

So here is an example conclusion for Sofia's results.

Don't worry if yours isn't exactly identical to this as long as it covers the same points.

So the best lubricant Sofia tested was Swish because with Swish the mass travelled furthest.

So Swish must have produced friction the most.

You can see from the table that the mass went 92 centimetres with Swish so it must have reduced friction the most, allowed the mass to slide to the furthest, that's why it's the best lubricant.

And the worst lubricant Sofia tested was Easy-glide because the mass travelled the smallest distance so Easy-glide must have reduced friction the least.

So well done if you've got something along those lines.

So we're now ready to look at the final section of the lesson, which is we're gonna have a look at applying what we've learned about lubricants and friction to real life 'cause, of course, that's what scientists do.

Scientists don't work outside of real life, scientists are working on real-life problems and what they find out can be really helpful to manufacturers, businesses, and people.

So we'll start with a quick reminder about what lubricants are and how they work.

Lubricants work by keeping surfaces slightly further apart so microscopic bumps catch on each other less or not at all.

And of course the microscopic bumps is what causes the friction forces.

So if the surfaces are kept slightly further apart so the bumps catch on each other less, then that's how lubricants reduce friction.

So let's do a quick check of that.

Complete the sentence to explain how lubricants work.

Lubricants keep surfaces slightly, what do they do? So the microscopic what catch on each other less? Have a go at filling in those blanks.

Five seconds, off you go, I'll go through some feedback.

Lubricants keep surfaces slightly further apart.

Anything along those lines will do.

Lubricants keep surfaces slightly further apart so the microscopic bumps on the surfaces catch on each other less.

That's how lubricants reduce friction.

Well done if you've got that.

So what should a good lubricant do? In real life, a good lubricant needs to reduce friction forces as much as possible but a good lubricant also needs to stay in place.

It's no use if it just falls off where it's supposed to be.

And a good lubricant should also not cause rusting of metal parts.

So, in reality, water's often not used as a lubricant because water can promote rusting.

And of course a big benefit of lubrication is it reduces the damage due to wear and tear when surfaces or moving parts are constantly rubbing on each other or moving past each other.

The unwanted friction forces are reduced by a lubricant, so that reduces wear and tear over time if a lubricant is used.

So let's do a little check of that.

Which pictures show a helpful or valuable use of a lubricant? A, B, and C.

Choose which pictures you think show a lubricant being helpful or being valuable in real life.

Five seconds to decide.

Okay, I'll go through some answers.

The snowy slush on the road is not being helpful because it's stopping those tyres from gripping on the roads so that's not helpful.

But the car engine oil is useful because that keeps moving parts slightly further apart from each other, so there's less wear and tear on the moving parts 'cause of car engine oil.

Oiling a squeaky hinge, well a squeaky hinge is probably annoying, the noise it makes every time you open or close the door, whereas oiling that squeaky hinge reduces the friction and maybe stops the surfaces rubbing on each other and causing that noise so you're not annoyed anymore.

So that's useful and valuable as well.

Well done if you've got both of those two as helpful or valuable uses of lubricants in real life.

What do you think could happen if a bike chain was never oiled? There's four options here, so choose as many as you think that could happen if a bike chain was never oiled.

I'll go through them each in turn, you can decide.

A, if a bike chain was never oiled, you would need to pedal with greater force to go at the same speed.

Is that true? If a bike chain was never oiled, this is B now, if a bike chain was never oiled, then the chain and cogs might wear down quickly over time.

C, if a bike chain was never oiled, then the chain might be noisier.

And D, if a bike chain was never oiled, then pedalling could be less smooth as you ride your bike.

Which do you think are true? Five seconds now to finalise your answers.

So I'm gonna give some feedback now.

In fact, all of these are true.

If a bike chain was never oiled, you would need to pedal with greater force 'cause friction is bigger so it's a bigger force to overcome.

The chain and cogs might wear down over time, the chain could be noisier, and peddling could be less smooth.

So lubricants can be very helpful in real life.

Time to try and put together everything we've learned about friction from the experiment and the analysis and how it applies to real life.

So this question is about snowboarding.

Snowboarders can add a lubricant to the underside of their snowboard.

You might wanna have a think about why that would be.

Now your job, your task here, is to write a short article for a snowboard magazine that explains what a lubricant is, we've covered that.

The benefit of lubricating a snowboard, we've just gone over lots of benefits of lubrication.

You might wanna think about which ones apply most for a snowboarder snowboarding downhill.

You should also include in your article how a lubricant works.

And, finally, you should include which lubricant from the table here would be your best buy and why.

So imagine you're a product tester and you've tested those lubricants, doing the same experiments that was shown where masses were flicked over a lubricated surface.

And we've looked at, we tried to look at which lubricant is gonna reduce friction the most.

And the table should tell you that and that should be your best buy for the snowboarders.

The lubricants are all the same price, so you don't need to worry about that in your article.

And the article must engage readers, which are gonna be snowboarders, but that article's also gotta be written using kind of professional language.

And you could start off your article by just saying this week I've been testing, as if you're a journalist who writes a article where you test out snowboard kit every week.

So this week I've been testing lubricants to put on the bottom of your snowboard and then talk about what a lubricant is, the benefit of lubricating a snowboard, how a lubricant works, and which lubricant from the table would be your best buy and why.

So that should take you a good bit of time.

You should put some really good effort into writing this article.

So you should pause the video now, make sure you've got a good pen, and take your time to write a really good article that covers all four of those bullet points.

Off you go.

Well done for your effort with that task summarising your work on lubricants and friction.

I'm gonna go through some feedback now.

So here's an example article, part one, I've split it into two parts.

So remember this article was supposed to explain what a lubricant is and the benefit of lubricating a snowboard.

And there are two other things which I'll show in part two.

So here's my example article.

This week I've been product testing lubricants that will help get you that extra speed down the slopes.

Lubricants reduce the friction between two surfaces, such as the bottom of your board and the snow.

That explains what a lubricant is, they reduce the friction between two surfaces.

The final sentence here is that friction forces oppose motion, so with a smaller friction force you'll slow down less and speed up more, making for a more exciting ride.

So that's the benefit of lubricating a snowboard, it's all about reducing the friction force so you go faster.

Here's part two of the article.

This part covers how a lubricant works and which lubricant from the table would be your best buy.

So lubricants work by keeping the surface of your board slightly further away from the snow, so the microscopic bumps on the bottom of your board catch less as your board slides downhill.

That's how a lubricant works.

So you should have covered, hopefully, that idea in your article.

And then the final couple of sentences are about my best buy from the table.

My best buy lubricant is Swish.

It's the same price, but our test showed it reduced friction much more because masses we tested could glide for a much longer distance when the surface was lubricated with Swish.

So that explains which would be the best buy and why by referring to an experiment that was done.

So very well done for your effort on this lesson on reducing friction.

Let's go through a summary of what we've gone through this lesson about how to analyse results to do with friction experiments.

So bar charts are used when the variable you've changed is categoric and line graphs are used when the variable you've changed is continuous.

We know that an effective lubricant reduces the friction force, so look at the size of the red arrow when you've got the lubricant in place in that right-hand picture.

A conclusion states what you found out in an experiment and also explains how you know.

And, finally, conclusions can be applied to real-life situations.