ingridscience

Distribute glass of water, flashlight and white paper to each student or student pair.
Ask them: We have water and sunlight. What weather feature might we make?
Once they know they are looking for a rainbow, older students can be challenged to arrange the flashlight, jar and paper to make a rainbow, while younger students can be assisted in making one:
Hold the jar in the air just above the desk. Lay the paper down in front of the jar. Shine the flashlight at the water line from back a bit, maybe angling it downwards a little. Don't block the bottom edge of the jar with your fingers. The higher the jar, the wider the rainbow. If you tip the jar slightly, you can make multiple rainbows.

Show students the materials.
Give them their challenge: make a device that turns when they blow on it.
(They can be tested outside in the wind, but this is less reliable and satisfying.)
They do not need to make a stand for it - have them focus on the mechanics of the spinning part.

For younger/less mechanically-minded students, explain the key design components:
A 'pivot': parts that can rotate around each other.
'Blades' that can catch the wind: larger surface areas that the wind can hit and push against.
It is useful to refer back to these if students get stuck in their designing.

Optionally show different ideas for making a pivot (see second photo):
1. a skewer in an inverted tube/pen cap (to which the blades can be attached)
2. a skewer through a straw (to which the blades can be attached)
3. a blunt pin through an enlarged hole in a straw
There are other ways to make a pivot, but these are simple ones I have seen so far.

For some student groups the design components may be best introduced sequentially.
First all students make a pivot, then share each others’ designs.
Then students choose any of the pivot styles displayed, make their own pivot, then design blades to attach to their pivot.

For older and more mechanically-minded students, they can work with the materials for a while, before naming/explaining the parts.
After a while, naming and explain the design elements of 'pivot' and 'blades'. This will help students that are still to start on a design, and conceptually frame designs already in progress.

For Kindergarten students, provide them with tube-and-skewer pivot, cardboard, scissors and tape. Demonstrate how the tube spins on the skewer. Draw and name shapes that they could cut out of cardboard ('rectangle' and 'triangle' good to include), to tape to the tube. They can add more shapes if they want. Depending on how they tape the blades onto the tube, and so how floppy the blades are, they may need to be shown how to strap a strip of curved cardboard across two blades to hold them steady.

Allow students time to freely experiment, discuss ideas together (and share good ideas with each other, as all designers and architects do).
The Play-Debrief-Replay method for teaching works well for this activity - see notes in the resource.

If students are in need of help, either ask them to visit other wind machines that are spinning in the classroom, or help them focus on some ideas (e.g. see pivot ideas above).

Once they are done experimenting, review the different ways of making the key machine elements (pivot; blades to catch the wind)

During discussion, refer to uses of machines that turn in the wind:
Wind turbines are used to generate electricity: the energy in wind turns a blade which runs a generator to make electricity. Wind turbines are in greater use with increasing sustainable energy practices. Wind turbine diagram of parts: https://upload.wikimedia.org/wikipedia/commons/thumb/6/6c/Wind_turbine_…
Wind pumps are wind machines that can be used to pump water for farming or for groundwater extraction. Photo of a wind pump: https://en.wikipedia.org/wiki/Windpump#/media/File:Wind-powered-agricul… Video showing wind pump mechanisms of gears and pump: https://www.youtube.com/watch?v=BugXmDxC0WM
Windmills were commonly used for grinding grain. They are complex machines of levers, wheels and gears. Windmills in the Netherlands: https://en.wikipedia.org/wiki/Windmill#/media/File:KinderdijkWindmills… Windmill diagram showing gears transmitting wind energy to millstones: https://tringlocalhistory.org.uk/Windmills/images/03/Schematic%202.jpg
Anemometers measure wind speed - cups that spin around a shaft. Using magnets, the number of turns is translated into wind speed.
Wind vanes have a blade that turns in the wind, but its position stabilizes to show the direction that the wind is coming from.

We will make a barometer to measure changes air pressure. Air pressure is caused by the molecules of air piled up on top of each other and pushing down. We do not normally notice these changes, but may have done if we have been in an airplane. The air pressure is quite a bit lower up high, so much so that airplane cabins need to be artificially pressurized so that we can breathe up there.

How to make a bottle barometer, which can show changes in air pressure:
Add the water to the empty drink bottle. Optional: add several drops food dye.
Insert the tubing into the bottle until one end rests on the bottom of the bottle and the other end hangs out of the bottle.
Suck on the tubing end outside of the bottle, until the water almost reaches your mouth.
Take your mouth off the end of the tubing and immediately plug the end with some clay/playdough. If the water level inside the tubing drops out of sight before plugging with clay, retry until the water line is high enough up the tubing to be clearly in view.
Watch the level in the tube for a little while to make sure the modelling clay makes an airtight seal on the end of the tube.
Add a piece of tape to the outside of the tube with a line on it, or on the wall next to where it is taped, to show the initial level of the water.

The level in the tubing will rise up and down as the atmospheric air pressure changes over several days:
Air pushes down on the water surface inside the bottle, which holds the water up in the tube.
If the atmospheric air pressure rises (usually associated with clear weather), the air pushes down more on the water surface inside the bottle, which pushes the water level further along the tube.
If the air pressure drops (usually associated with rainy weather), air pushes down less on the water surface inside the bottle and the water level in the tube will drop.

To immediately see how the water level in the tube changes, use your breath to change the air pressure inside the bottle:
Cut a straw in half and wrap more modelling clay around it, sealing to make sure that there are no air gaps.
Insert the straw into the barometer bottle mouth, and use the clay to seal over the top of the bottle and around the tubing.
Blow into the straw. If their is no air leakage, you will make the air pressure in the bottle rise, which will push the liquid up the tubing.
It takes a lot of puff to move the water line only a little. This gives a sense of the pressure changes that occur in our atmosphere regularly, but we do not notice so much (unless we have arthritis which can cause sensitivity to pressure changes in the joints).

To watch atmospheric air pressure change over time, tape the tube onto a nearby wall. Check regularly, especially when the weather is changing to see the liquid level rise or fall.
Clear weather is associated with higher pressure because local high pressure air will move outwards away from the high pressure region to lower pressure regions around. This air is replaced by air from above.
Rainy weather is associated with lower pressure because local low pressure means that surrounding higher pressure air will move inwards. Then it is forced upwards. The rising air cools and water condenses out forming clouds and often bringing rain.

Follow instructions from this activity from the Exploratorium, also attached, and summarized below:
https://www.exploratorium.edu/pie/downloads/Cardboard_Automata.pdf

In brief:
Make a frame from a cardboard box, with triangles to reinforce inside the corners. Note: do not make the frame too large, or there will be too much play and the cams won't mesh. About 20cm wide and 15cm high works well.
Stick a skewer (a "shaft") horizontally through the frame, adding a circle of foam (a "cam") to it, the placement of the hole in the cam depending on which mechanism(s) you want to make. See the attached file from the Exploratorium for ideas. It is best if the cam is at least 5cm diameter.
Add another foam cam on a vertical shaft through the top of the box that will rest on the first circle. Don't make this skewer too long or it will move sideways. A straw glued into the box to guide the skewer helps keep it upright. Washers, or modelling clay, give some weight to the cam so that it always rests on the lower cam.
Depending on where the horizontal shaft goes through its cam, the upright shaft will move round and round, or round and round and up and down.
Optional: add another circle on the horizontal shaft to make the upright shaft also go back and forth.
Decorate the upright shaft, so that the movement(s) is/are highlighted.

Students hammer nails around the edge of the board, with a curve at the top. Stretch elastic bands over to make a wall around the board.

Make the marble launcher: slide the spring onto the nail then insert the nail through the drywall anchor. Attach the launcher to the bottom corner of the board, inside the wall (right or left side, depending on the handedness of the student), using a staple. Add a blob of hot glue (or an elastic band wrapped tightly) to the end of the nail that is pulled, to stop it from leaving the shooter when it is released.

Make a channel for the marble to travel up after it is released.
Add more nails and elastic bands to the board as desired to make obstacles for the marble.
Add scoring boxes at the bottom of the board.

After students have played with their own pinball machine for a while, sit in a cirlcle to try each others:
Start with each student with their own machine in front of them, then altogether pass to the next student (all in the same direction). Students can keep their own marble to use on all the pinball machines. Keep passing until the students end up with their own machine in front of them.

See saw
Set up the see saw with the 2X6 centred on the split log.

Ask a pair of students to experiment with the see saw. They can either lift a large block (in the photo), or they can try lifting each other. (The objects are heavy, so the students should work slowly and carefully with good communication within the pair). Prompt the students to move the fulcrum and see what difference it makes.
They should find that when the fulcrum is near the load/student, they are easy to push it up in the air, but when it is far from the load, it is very hard (if not impossible).

Students can draw what they discover using standard notation:
The lever arm (plank of wood) is drawn as a straight line, and the fulcrum is a triangle under the line in the correct position. Use arrows to show where force is applied (at one end of the see saw - also called the effort), and where the resulting force is felt (under the concrete weight - also called the load).

Ask the students how the height of the ends of the see saw varies as the fulcrum is moved. They can measure the distances for more accurate recording of the results.
Less force over a greater distance (with the fulcrum near to the weight) is an easier way to lift the weight. However, in this case the weight will not move as high.
The amount of work balances: less force over a greater distance (at one end of the lever) balances more force over a smaller distance (at the other end).

Lifting a rock
Use a long 2X6 or 2X8 as a lever, and a split log as a fulcrum. If students have already experimented with fulcrum placement, ask them to tell you where the fulcrum should be placed to lift a very heavy object [it should be placed very near the rock]. With this arrangement a large rock can be lifted up a few centimetres (higher could be dangerous incase the rock slips sideways) by a child.

Optional: show photos of how people have been using levers for lifting heavy things for thousands of years.
Egyptians used long sticks as levers to move stones e.g. when making pyramids, evidenced by mortises (holes in stones placed for lever use). Try this image link:
https://krisdedecker.typepad.com/.a/6a00e0099229e8883301310fcb6a12970c-…
Indigenous North West Coast large houses are built using levers to raise the massive cedar logs. See page 113 of "Knowing Home: Braiding Indigenous Science with Western Science, Book 1". Try this link: https://greatbearrainforesttrust.org/wp-content/uploads/2018/05/Knowing…
Archimedes proved by math and geometry how a lever functions, and was quoted as saying "Give me a place to stand and I shall move the world". Try this link for a famous etching: http://www.thwink.org/sustain/glossary/images/LeveragePoint_ArchimedesL…

Lifting a marble, or small load, up high
Can also use to lift a smaller weight high with a heavier weight - see the photo of the upturned chair supporting a lever.
A pot of water is used to lift a marble up high - students were challenged to use a pot of water to lift a marble to table height.
The marble can be successfully lifted when the fulcrum is very near the bucket of water, so that the other end holding the marble can swing up high enough to reach the table top.
Review how a lever works: a lot of force at one end moving a small distance (the bucket full of water) produces a smaller force over a greater distance at the other end (hence the lighter load of the marble can be lifted high enough to reach the table top).
Relate to other levers students might be familiar with e.g. see saw.

Before the class
The teacher should understand the set up of the different pulley systems (image at https://en.wikipedia.org/wiki/Block_and_tackle#/media/File:Tackles.png):
A single fixed pulley has one pulley at the top with a string over it.
A gun tackle has a single fixed pulley at the top and a single pulley at the bottom (which will move). The string is tied off at the top, wraps around the bottom pulley then around the top pulley. Result is that two strings are pulling up on the bottom pulley (and the weight attached to it).
A luff tackle has a fixed double pulley at the top and a single pulley at the bottom (which is moveable). The string is tied off at the bottom pulley, wraps around the top pulley then the bottom pulley then the top pulley again (in the second groove). Result is that three strings are pulling up on the bottom pulley (and the weight attached to it).
A double tackle has two double pulleys, top and bottom. The string is tied off at the top, wraps around the bottom, then top, them bottom, then top pulley (using a new groove each time). Result is that four strings are pulling up on the bottom pulley (and the weight attached to it).

After my experimenting, I recommend using a single fixed pulley, a gun and a double tackle so that the change in forces is clear.
I made this activity a demonstration for primaries, with one of each pulley system that the class looked at together.
I recommend only asking grade 7s and dextrous 6s to set up their own systems (give them a system to copy). For intermediates, I made a set of 9 pulley systems (three of each kind), and placed them around the classroom for intermediates to try in turn.

Optional: no-pulley system
Simply pass the string over the bar, attach a cup to each end, and see how many counters it takes to lift another cup of counters.
Because of the friction between the bar and the string, it will take more counters in the top cup to lift the bottom cup.
One of the functions of a pulley is to provide a low friction system, with a wheel that turns.

Single fixed pulley
Hang one pulley from the bar, pass the string through it, then attach cups at each end, so that one cup is on the floor and the other is next to the pulley. Coil up extra string and add it into the clip that is holding the cup. Add (maybe 8) counters to the bottom cup, and then slowly add counters to the top cup until it moves the bottom cup upwards. [There should be about the same number of counters in each, maybe a couple more in the top cup.]
A single pulley simply changes the direction of a force. Show images of flag poles and window blinds where fixed pulleys change the direction of a force.

Composite pulley systems (with fixed and moveable pulleys)
Set up the other systems with one cup hanging from the bottom pulley. Attach it with a mini binder clip (take the arm off a mini binder clip, pass it though the bottom eye of the pulley, then reattach arm). And another cup to the free end of the string, pulling the string through until the bottom cup is on the floor and the top cup is next to the top pulley. Add (maybe 8) counters to the bottom cup, then slowly add counters to the top cup. Count how many counters are needed in the top cup (the "effort") to pull the bottom cup (the "load") upwards, for each system.
See attached worksheets for recording this data. (An added complexity is that the top cup effort is pulling up the weight of the pulley as well as the counters in the bottom cup. If the pulleys are light, this weight can be discounted, but if they are as heavy as several counters, the results need to take this into account.)

Transcribe all the data to the board for discussion. Students will (hopefully) see that the gun, luff and double tackle require relatively fewer counters in the top cup to raise the bottom cup, than the single fixed pulley. If the data is clean, the tackles with the greater number of strings pulling upwards will require the fewest number of counters.
Getting more complicated:
The ratio of the load/effort can be calculated to see how it changes with more wraps of the string: the ratio is greater with more wraps of the string i.e. less load is required as the number of wraps goes up (from single pulley, to gun tackle to luff tackle). In a perfect system the ratio would be the same as the number of string lengths i.e. ratio of 1 for single pulley, 2 for gun tackle and 3 for luff tackle.

A greater number of wraps of string provide a mechanical advantage: a greater load can be lifted with the same effort but more string is pulled through.

Show students images of fixed and moveable pulleys.
A flag pole uses a single fixed pulley. Cranes use many wraps of cable to provide a large mechanical advantage and allowing very large loads to be lifted, as well as fixed pulleys to change the direction of the force. Boat rigging allows one person to pull in sails that would be too hard without the aid of moveable pulleys. Crevasse rescue systems use a pulley set-up which includes fixed pulleys to change the direction of the force, moveable pulleys to trade force for distance and hitches which clamp ropes.

We use water to turn wheels to make electricity (hydroelectricity), catch fish (fish wheel) or grind flour.

Pour water over a wheel to show how it turns.

Optionally lift an object from the floor to the table top, using the force of falling water on the water wheel.

Before the class, prepare discs from the pie plates for the students, as cut edges are sharp:
Carefully cut out the flat part of the pie plate and discard the sides.
Punch a hole exactly in the centre with a pencil and enlarge slightly.

Students make cuts from the edge of the pie pan 2/3 of the way to the centre, in four or six places (to start, try modifications later). Fold over the sides of each section to make a paddle wheel shape.

Wrap a small piece of foam around the wooden rod and tape it in place. Push the rod through the hole in the pie plate, enlarging the hole until the plate fits snugly on the foam around the rod. The plate should not turn easily at all without the rod (the axle) turning.

Tape U-shaped pieces of foam to the centre of each of the short sides of the tray.
Lay the wheel and axle over the foam supports on the tray. Test that it can turn without hitting the bottom of the tray. If necessary, fold over the outside edges of the pie plate.

If objects are to be lifted with the falling water, make sure one end of the rod protrudes over the edge of the tray more, then tape the string to this end of the rod. Cut the string off where it meets the floor, and tie on a small weight e.g. the scissors.

Pour water from the 2L bottle onto the wheel. The weight of the water hitting the paddle blades generates a force which makes the blades move and the wheel turn.
Once the water runs out, pour the tray of water back into the bottle (using the funnel) for reuse.

If a weight is being lifted, the turning wheel turns the rod, which winds the string and pulls up the weight.
Challenge student to control how they pour the water to make the weight raise slowly or faster.

In a traditional water mill, a water wheel turns grindstones to make flour:
https://www.youtube.com/watch?v=1L5Pt4BLeos

A fish wheel turns in the moving water of a river and has attached netting to catch salmon:
Image here: https://gallery.janeandjohn.org/index.php/haines/FishWheel and in here: https://salmonlife.org/archived/stories/copper-river/
https://www.youtube.com/watch?v=-l81d3R1-OY
https://www.youtube.com/watch?v=uPoKHOMlhZ0
Fish wheels are used to catch salmon during a run, either for food or for tagging (to track salmon populations).

Hydroelectric power is made from a water wheel (called a turbine):
image: https://www.energy.gov/sites/default/files/styles/full_article_width/pu…
Video: https://www.youtube.com/watch?v=OC8Lbyeyh-E