Wind Lab teaching notes

About these lessons

Four lessons of about forty-five minutes each, for ages eleven to fourteen. Students put things in a wind tunnel and read the push on a scale, draw a shape that pulls less than a teardrop, send a gale down a street and find out what slides, tips and flies, and run a wind turbine through a week with a hurricane in it.

You do not need to have used Wind Lab before, or to know any physics. Everything you are asked to say or point at is written here, in the words that are on the screen. The numbers quoted are the ones the lab shows, in mph and pounds; a class that works in km/h and newtons will see different numbers that mean the same thing.

How to read this guide

Each lesson is a row of short parts, and each part has the same five headings:

1. Say what to tell the class, in a sentence or two. Use your own words if you like.
2. Students do the steps, in order. Read them out or put them on the board.
3. On their screens what you should see when you walk round. If a screen does not look like this, that student needs you.
4. If it goes wrong what usually goes wrong at this step, and the way out.
5. Ask a question for the room. The point is the talking, so take two or three answers and do not give yours.

The four lessons

Before the first lesson

• Every student needs Wind Lab open in a browser, with a mouse or a trackpad. It runs on a Chromebook. Nothing is installed.
• Work is kept as the student goes. There is no save button to forget.
• No lesson needs sound. The hum of a wire in lesson 1 is an extra, and it is quiet.
• The lab shows mph and pounds, or km/h and newtons. The two buttons at the top, mph lbf and km/h N, switch between them. This guide gives the mph numbers.
• Try lesson 1 yourself first. It takes ten minutes, and you will have met every button the class will meet.

The screen. These are the names this guide uses, and they are the words on the screen.

Lesson 1: The push of the wind

Lesson 1: The push of the wind: Double the wind (0 to 10)

1. Say This is a wind tunnel. The box on the left is the test section, the fan is off the left edge, and the scale under the cube reads how hard the wind pushes on it. Today you find out what that push depends on.
2. Students do Open Wind Lab. It opens on the Tunnel with a cube on the left and a teardrop on the right. Press One thing only so only the cube is left. Drag the dial under Wind to 15 mph and write down the scale's number. Then drag it to 30 mph and write that down.
3. On their screens At 15 mph the scale under the cube reads about 1.63 lbf. At 30 mph it reads about 6.50 lbf. The dashed smoke lines bend around the cube, and a circle turns behind it: that is the wake.
4. If it goes wrong The scale reads 0: the dial is at calm. A student who sees newtons has pressed km/h N; that is fine, the doubling works the same. The number is hard to land exactly: close is fine, the lab also prints the push in the Reading card on the right.
5. Ask The wind went up twice. How many times did the push go up? What would it be at 60 mph? (Four times, and about 26 pounds: the push goes with the square of the speed.)

Lesson 1: The push of the wind: The cube and the teardrop (10 to 20)

1. Say Now the same wind on a different shape. The teardrop is the same height as the cube, so the wind meets the same area. Guess before you look: how much less will it pull?
2. Students do Press Compare with another, then press teardrop on the shelf. Set the dial to 30 mph. Read both scales. Then press Change the second thing and try sphere, then flat plate.
3. On their screens Two test sections side by side. At 30 mph the cube reads about 6.50 lbf and the teardrop about 0.25 lbf; the card between them says The cube pulls 26 times what the teardrop pulls at the same wind and the same size. The sphere reads about 0.62 and the flat plate about 7.9. The smoke behind the teardrop closes up; behind the cube and the plate it churns.
4. If it goes wrong The second section did not appear: the shelf press went to the first thing. Press Compare with another first, then the shelf. Each section has its own scale; the number under Reading is the first thing's.
5. Ask Same wind, same size. What is different about the teardrop? Look at the smoke behind each one. Where does the push come from?

Lesson 1: The push of the wind: Thin air (20 to 30)

1. Say The wind is moving air, and air has weight. What if the air were thinner? Let us take the tunnel up a mountain.
2. Students do Press One thing only so the cube is alone at 30 mph. Under Air, press a mile up, then a mountain pass, then sea level again. Watch the scale each time.
3. On their screens At sea level the cube reads about 6.50 lbf. A mile up it drops to about 5.45 lbf, and on the mountain pass to about 4.45 lbf. The line under the chips says what a cubic foot of the air weighs each time.
4. If it goes wrong Nothing changed: the student is on the Shape bench, where the chips are different. Press Tunnel.
5. Ask The wind is the same speed. Why does it push less up the mountain? What else gets harder to do up there?

Lesson 1: The push of the wind: The rule behind the scale (30 to 45)

1. Say The scale follows one rule, and you have now met every part of it: the air's weight, the speed squared, the area, and the shape number. The lab will show it with the numbers filled in.
2. Students do Tick All at the top right. In the Reading card, find the line that starts push = ½ ×. Change the dial and watch the line change. Then press sphere and turn the dial up to 60 mph and beyond, watching the line that starts Reynolds number.
3. On their screens A small line under the reading: push = ½ × 1.225 kg/m³ × (13.4 m/s)² × 1.05 × 0.25 m² = 28.9 N, in metric even for a class in mph, since that is the units the rule is written in. For the sphere past about 60 mph the orange shape number falls from 0.47 toward 0.10 and the card says the sphere is past its drag crisis.
4. If it goes wrong The All view shows a lot. Point the student at the one line that starts push =. A student who finds the sphere's falling number confusing can leave it: it is a bonus, and the golf ball on the shelf is the same story for lesson 2's fast finishers.
5. Ask Which part of the rule is squared? If a sign is twice as wide, is the push twice or four times? If the wind is twice as fast?

By the end, each student can say:

• I doubled the wind and saw the push go four times up.
• I can say why a teardrop is pushed less than a cube the same size.
• I can name the four things the push depends on.

Lesson 2: Design the shape

Lesson 2: Design the shape: The box and the starters (0 to 10)

1. Say Yesterday the lab gave you shapes. Today you draw your own. Everyone gets the same box, so the only way to pull less is the shape.
2. Students do Press Shape. Under Start from, press box, then ball, then cone, then teardrop, reading the orange shape number each time. Then press flip top to bottom on the teardrop.
3. On their screens A long box with a grid, the shape in it with yellow dots on its outline, dashed smoke around it. The numbers: box 1.05, ball 0.47, cone 0.47, teardrop 0.040. Flipping changes nothing, because the wind comes from the left either way. The list on the right, Lowest number wins, ranks them.
4. If it goes wrong The dots are missing and the hint says made by the formula: the student pressed a formula. Press drawing under Make it by.
5. Ask The cone has a point at the front and the ball is round, and they score the same. The teardrop is round at the front too. So what is the teardrop doing that the ball is not?

Lesson 2: Design the shape: Beat the ball (10 to 25)

1. Say Start from the box and make it pull less than the ball, 0.47. Drag a dot to move it. Tap an edge to add a dot. Double-tap a dot to take it away.
2. Students do Press box. Drag the two front dots toward each other to make a nose. Read the number. Then work on the back: drag the two back dots toward the middle line, and add dots along the top and bottom edges to make the taper longer.
3. On their screens The number changes as a dot moves. Rounding or pointing the front takes the number from 1.05 straight down to about 0.47, and no further: the card under Reading says Front pointed, back blunt. Only when the back closes gradually does it fall below the ball, and the card changes to back a short taper, then a long taper. your shape appears in the ranking in blue.
4. If it goes wrong The outline crossed itself and the number jumped: press Undo. A dot landed on top of another: double-tap one of them. A student who has made a mess: press box and start again.
5. Ask You made the front pointed and the number stopped at the ball's. What did you have to change to get below it? Why does the front stop helping?

Lesson 2: Design the shape: Beat the teardrop (25 to 40)

1. Say The teardrop is 0.040. The box is only so long, so a longer taper means a smaller front. See how low you can go, and write down the number and what you did.
2. Students do Keep working on the shape, or press teardrop and improve it. Fast finishers: press a formula under Make it by, press teardrop there, and change the number 25 in the first line to 15.
3. On their screens Numbers below 0.040 are possible with a thinner, longer teardrop; the lab floors at 0.040, so two shapes can tie. In the formula view, the shape is drawn from the four lines of code, with no dots; the line under the code says It reads. Shape number 0.040, or names the line that does not read.
4. If it goes wrong The formula says Line 2: and an error: the student broke the line while typing. Press teardrop under the formula to get it back. A shape that is nothing but a line reads 1.17: that is a flat plate, and it is right.
5. Ask Two shapes both read 0.040. Are they the same shape? What would a real tunnel need to tell them apart?

Lesson 2: Design the shape: Show and tell (40 to 45)

1. Say Three people show their shape and say one thing they changed that mattered.
2. Students do Three students come to the front, or share their screens. Everyone else writes down the lowest number in the room.
3. On their screens The Lowest number wins list, with your shape somewhere in it.
4. If it goes wrong A student's shape vanished: it is still there, press Shape. Shapes are kept as the student goes.
5. Ask Cars, trains and bicycle helmets are all shaped for this. Where on a car can you see the long taper, and where can you not, and why not?

By the end, each student can say:

• I drew a shape in the same box as everyone else and read its number.
• I beat the ball, and I can say what I changed at the back to do it.
• I can say why the back of a shape matters more than the front.

Lesson 3: What blows over

Lesson 3: What blows over: Send the wind (0 to 10)

1. Say Same wind, but now it meets real things: tents, a chair, a trash can, a tree, a person. The wind rises from nothing to the speed on the dial, and each thing goes when the push is enough.
2. Students do Press Street. Check that the campsite is picked under Street. Set the dial to 45 mph and under Gusts press gusty. Press Send the wind and watch for ten seconds.
3. On their screens The flag on the pole fills, the wind streaks thicken, and things go one by one: the loose tent tumbles off to the right first, then the open trash can, then the chair, then the staked tent on a gust; the tree comes down; the person leans and steps back. Under each place a thing stood, the speed it went at stays written. Nothing happens until Send the wind is pressed; before that the list on the right says what each thing would do.
4. If it goes wrong Everything vanished in a flash: the dial is very high. Set it to 45 mph and send again. The run is nine seconds; press nothing until the flag stops filling.
5. Ask What went first, and what never went? Before you read anything, guess why.

Lesson 3: What blows over: Read the sentences (10 to 20)

1. Say Every thing has a sentence that says what happened and the two numbers that decided it. Find the tent's.
2. Students do Scroll the right-hand panel to the list under Send the wind. Read the sentence for tent, not staked, then tent, staked, then a person standing.
3. On their screens Tent, not staked was carried away at 15 mph, and the sentence says the push matched its weight, 7.7 pounds. Tent, staked went at 64 mph, on a gust: the stakes pull out of the grass, and then it was carried too. A person standing had to lean hard and step back at 42 mph, a push of a fifth of their weight, still standing. The tree in leaf went at 58 mph: the roots let go.
4. If it goes wrong The sentences say what a thing would do instead of what it did: the wind has not been sent since the last change. Press Send the wind.
5. Ask The staked tent weighs the same as the loose one. Why did it last to 64 mph? What is the gust doing in that sentence?

Lesson 3: What blows over: Slide or tip (20 to 30)

1. Say Two ways to go without flying: slide along the ground, or tip over. A low, heavy thing slides. A tall, narrow thing tips. Let us look at the trash can.
2. Students do Press empty street. On the shelf, press lid on under trash can. Set the dial to 30 mph, steady, and press Send the wind. Then tick All, press the can in the list, and read the line of speeds under its card.
3. On their screens The can slides at about 21 mph. In the All view its card lists all three ways it could go: slides at 21 mph, tips at 26 mph, carried at 35 mph, each with the push it needs. The card also shows a slider for its weight and one for its base width.
4. If it goes wrong The can did nothing: the dial is under 21 mph. The list on the right says what it would do and at what speed. A student who cannot find the can's card: press the can on the street itself.
5. Ask The can slides before it tips. What would make it tip first instead? (A narrower base, or a grippier ground.) What makes a thing slide later?

Lesson 3: What blows over: Make it hold (30 to 45)

1. Say Now you are the one setting up the campsite before a storm. Pick a thing, change one thing about it, and make it hold at 45 mph.
2. Students do Press the campsite. With All ticked, press a thing in the list and move its slider: the weight of a tent (gear inside), the stake hold of the staked tent, the weight of the chair. Set the dial to 45 mph, steady, press Send the wind, and read the line that says Last time against This time.
3. On their screens After the second run the panel says Last time, at 45 mph steady: 4 of 6 went. This time: 3 of 6, or whatever the change did. A tent with 40 pounds of gear inside holds through 45 mph; a chair weighted to 15 pounds still slides at about 35.
4. If it goes wrong The slider did not stay: it only shows with All ticked and the thing picked in the list. The Last time line needs two runs on the same street.
5. Ask What is the cheapest change that saved the most things? Campers put their gear inside the tent before a storm. Why does that work?

By the end, each student can say:

• I sent a wind down the campsite and can say what went first and why.
• I can tell a thing that slides from a thing that tips, and say what decides it.
• I changed one thing so it held at 45 mph.

Lesson 4: Run a wind turbine

Lesson 4: Run a wind turbine: Eight times the power (0 to 10)

1. Say A turbine takes power out of moving air. The push went with the square of the speed; the power goes with the cube, because faster air also brings more air past each second.
2. Students do Press Turbine. Check that farm turbine is picked. Set the dial to 11 mph and read the Reading card's first sentence. Then 22 mph, then 44 mph.
3. On their screens At 11 mph the card says the wind through the rotor carries about 22.9 kW; at 22 mph about 183 kW; at 44 mph about 1.46 MW. The big number at the top of the card is what this turbine makes: 9.8 kW, 78 kW, and then 100 kW at 44 mph, its generator's most. The chart in the middle shows the two curves bending up and the turbine's own line flattening.
4. If it goes wrong The card says below its cut-in: the dial is under 8 mph, and a turbine does not turn in that. The dial is shared with the other benches, so it may be where lesson 3 left it.
5. Ask From 11 to 22 mph the power went up eight times. Where did the eight come from, when the push only went four times? Why does the turbine's own number stop at 100 kW?

Lesson 4: Run a wind turbine: What a rotor can take (10 to 20)

1. Say The dashed orange line on the chart is Betz's limit: no rotor of any kind can take more than about six tenths of the wind's power, because the air has to keep moving to get out of the way. The best real rotors get about three quarters of that.
2. Students do Set the dial to 22 mph. Drag Blade pitch slowly from 0 to 90 and watch the big number and the blades.
3. On their screens At pitch 0 the rotor takes 45% of the wind's power, the line under the slider says, and the turbine makes about 78 kW. As the pitch rises the number falls; at 45 and beyond the slider says feathered, the blades turn edge-on and the turbine makes 0 W.
4. If it goes wrong The blades stopped and the student thinks it is broken: the pitch is feathered. Drag it back to 0.
5. Ask Why would anyone feather a turbine on purpose? When would a wind be too much?

Lesson 4: Run a wind turbine: The week with a hurricane (20 to 35)

1. Say Real turbines are run by rules: above a speed, feather; above another, brake. Here is a week of weather with a hurricane on the fifth day. The one rule written for you feathers the blades above 55 mph. Run it and see what happens.
2. Students do Set the pitch back to 0. Under Control rules, read the rule: when the wind is above 55 mph, feather the blades. Check that a week with a hurricane is picked. Press Run the week and watch the bars fill. Read the card.
3. On their screens Bars rise day by day, a strip under them turns from blue (running) to yellow (feathered) on Friday and stays yellow. The card says 90 points: 7.6 MWh made of 8.4 a perfect controller would have made, never past its cut-out, not wrecked, and the tip: Nothing turned it back on.
4. If it goes wrong The score is different: the pitch is not 0, or a rule was changed. Press Undo until the rule reads as above. The run takes twelve seconds; wait for the card.
5. Ask The turbine was safe and still lost a tenth of the week. What did the rule forget? What does a rule need to say to fix it?

Lesson 4: Run a wind turbine: Turn it back on (35 to 45)

1. Say Add the missing rule. Then, if there is time, take the first rule away and see what the hurricane does to a turbine nobody stops.
2. Students do Press + Add a rule and pick the first shape, when the wind is above 55 mph, feather the blades. A second copy of the rule appears. Press its blue words: change above to below, 55 to 45, and feather the blades to run. Press Run the week. Then press the × on the first rule and run again.
3. On their screens With both rules: 98 points, 8.2 MWh of 8.4, and the tip says a real controller lives in the same tradeoff. With no rules: the strip turns red on Friday, the card says wrecked, 100 points off, and lists the gust that did it.
4. If it goes wrong The blue words do not change: a menu opens under them; pick from it. A student who wants to type can press Text and write the line in the same words.
5. Ask Why not just set the feather speed very high and keep making power? What did the wrecked turbine make in the end?

By the end, each student can say:

• I saw the power in the wind go eight times up when the speed doubled.
• I can say what Betz's limit is and why a turbine is feathered in a storm.
• I wrote a rule that turned the turbine back on after the storm, and my week scored higher.

More help

Is something on this page wrong or not clear? Write to us.