Drag

03 Apr 2011

WALTDescribe what drag is and some examples of drag reduction in everyday life

Explain drag using the particle model

Carry out a fair test to investigate the relationship between shape and drag

KeywordsDrag The force of resistance acting on an object moving through air or water

Air resistance The force of resistance acting on an object moving through air

Water resistance The force of resistance acting on an object moving through water

Streamlined Something that has a smooth shape designed to reduce drag

What is a force?

A force is a …………. or a ………….

What is a force?

A force is a push or a pull.

A force can make something change

……………… or ……………….

A force can make something change

direction or shape.

What will the car do?

What are the forces?

What will the car do?

The car will accelerate!

Pull (engine force)Friction

+Air resistance

What will the car do?

Pull (engine force)Friction

+Air resistance

What will the car do?

Pull (engine force)Friction

+Air resistance

The car will move at a constant speed

Speeding Up

Why do things move?

FasterWhy are they wearing costumes?

Faster

Faster

What do these two images have in common?

Fuel consumption

Pages 134/135 of Exploring Science.

A lorry is traveling at a constant speed of 70mph• are the forces balanced or unbalanced?• what 3 forces act on the lorry? • if we reduce the air resistance, what is the effect on fuel consumption?• can you tell me 2 other advantages of lorries fitting deflectors

Fuel consumption

Pages 134/135 of Exploring Science.

A lorry is traveling at a constant speed of 70mph• are the forces balanced or unbalanced?• what 3 forces act on the lorry? • if we reduce the air resistance, what is the effect on fuel consumption?• can you tell me 2 other advantages of lorries fitting deflectors [cheaper food, less carbon emissions]

Wind tunnel/cyclist

http://www.bbc.co.uk/learningzone/clips/aerodynamics-reducing-air-resistance/276.html

While you are watching sketch the outline of any shapes you would like to test in our streamlining experiment.

Particle modelUsing the particle model to explain drag OK – now I want you to take 30 seconds to read the card in front of you in pairs. I suggest you each read alternate paragraphs. Now pick an A and a B – I want A to test B by asking the 5 questions in italic. Then switch. Continue until you are both answering all questions correctly.

Cyclists reducing drag

http://www.bbc.co.uk/learningzone/clips/air-resistance/10595.html 2minI would like you write down the 3 ways of reducing air resistance you see in this video, and at least 2 design features you see here that reduce air resistance.

InvestigationDo a fair test to investigate which is the best shape to reduce drag.

You have been given a worksheet on which to record your results.

You each have a cylinder of wallpaper paste, a beaker, a stopclock, plasticene, and a balance to weigh it.

GraphingDraw a bar chart of velocity vs. shape, placing the bars in order of velocity, so the slowest missile is first bar. Above each bar draw a small diagram of the shape.

Some: if you also did the range of masses, do a line graph showing velocity vs. mass.

Pack awayhttp://www.bbc.co.uk/learningzone/clips/the-sharkskin-swimming-suit/11036.html

WALTDescribe what drag is and some examples of drag reduction in everyday life

Explain drag using the particle model

Carry out a fair test to investigate the relationship between shape and drag

Drag is caused when water or air particles

Hit a moving object and bounce off it

Heat a moving object

Are very heavy

The amount of drag on a moving object depends on

The temperature of the object

The object’s speed and shape

The object’s speed

Drag on a lorry can be reduced by fitting a

Discriminator

Deflector

Terminator