Wind and Air Power
low RPM craft motor or windshield wiper motor (buying surplus or from a wrecker is cheaper!)
balsa wood or plastic from drink crystal lids
piece of dowelling, strong stick, old ruler or similar for post
clay for base (or set in plaster of paris in a yogurt tub or similar)
adult weilding a glue gun
self-hardening clay (enough to make a plum-sized ball)
optional: duct tape or white glue for affixing the motor to the post
- Cut out 5 blades from the balsa or plastic.
- Form the clay into a ball and flatten it slightly. Press the blades into the edges at a slight angle and evenly spaced. You can let the clay dry with the blades in place, or remove and then glue them into the slots you made when the clay has hardened.
- Poke an indent into the centre of the ball using the motor pin and remove the pin. Let the clay harden.
Set the post into the base and let set.
- Mount the motor onto the top of the post. You can use glue, duct tape or hardware to mount it, but be sure that it balances so that the post does not tip over. Your method will vary depending on the size and shape of the motor you use.
Use the glue gun to attach the blade assembly to the motor pin.
Wire the LED to the motor output. Now put the station in a windy spot and watch it generate power to light the LED.
Tip: if the LED does not light up, try reversing the wires to reverse the polarity. LED's only work in one direction.
2 chairs or other pieces of furniture to tie the ends of the string to
Optional: free-wheeling toy car (try making one with Lego or K'nex)
Optional: toy boat (homemade is good here too!)
First, to truly appreciate balloon power, you need to blow up the balloon and pinch the neck. Now release it and let the balloon fly. Try repeating this, pointing the balloon opening in different directions. What do you notice?
The inflated balloon is stored potential energy. The latex has been stretched, and the elasticity of it (potential energy) will cause it to contract back to its unstretched form, and in doing so force the air out of the opening. When the air is forced out, the balloon will move in the opposite direction, thanks to Newton's third law (for every action there is an equal and opposite reaction).
To make a balloon powered rocket:
- Thread the string through the straw, then tie each end of the string to a chair and spread the chairs apart to make the string taught.
- Cut a piece of sticky tap and drape it over the straw so it is ready for taping to the balloon.
- Blow up a balloon and pinch the end to hold the air inside.
- With the free hand, press the tape onto the balloon so it is fastened to the straw and the opening is facing the closest chair.
- Let go of the balloon and watch it go!
- Extensions: Try setting up two lines and racing balloon rockets. Try different shaped balloons--which ones are fastest?
- To make a balloon-powered car, tape the inflated balloon to the top of a toy car, let go and watch it move.
- To make a balloon powered boat, tape the balloon to the top of a toy boat.
- You can also try building the balloon right into the design of a homemade car or boat.
Pinwheel Weather Vane
modelling slay (small piece)
short pin or cigar-box nail
large square sheet of flexible plastic, cover stock or similar heavy paper (a plastic report cover works well) 8-10" (25-30 cm) is a good size
pencil, pen or marker
optional: markers, crayons or paint to decorate your pinwheel; a small-holed bead or two
- Plug the top of your straw with modelling clay so that the top 1-2 cm (1") or so is full of clay.
- Decorate your square as desired.
- Using your straight edge, draw a light line to connect the opposite corners of the square with a diagonal line. Repeat for the other corners.
- Cut from each corner inward along the line toward the centre, stopping about 2-3 cm away from the centre. Now you have 8 "corners".
- Fold one corner towards the centre and glue at the centre so that the point meets and slightly overlaps the centre of the square. Skip the next corner and glue the following inwards in the same manner. Repeat so 4 corners have been glued.
- Poke the pin through the centre of the square so that it pierces where the corners have overlapped. Now press the pin into the clay-filled section of the straw. If your pin is too long, try threading a bead or two onto it before piercing the square and the straw.
- Blow on your pinwheel from various angles. How can you make it move fastest?
- Extension: To turn this into a true weather vane, try and find a way to allow your pinwheel shaft to rotate so that it can catch wind from any direction.
Feeling the Pressure
Wind happens when an area of high pressure air moves to an area of low pressure air. Usually, the high pressure comes from air that has been heated by the sun. As the air is heated it rises and expands. As it cools, it loses pressure and takes up less space. Moving air also holds energy, and will have higher pressure than still air or air that is moving slower.
You don't have to take my word for it though--try these experiments and see for yourself.
a piece of notebook paper
a large sheet of newspaper
a long ruler (30 cm or longer)
a large table
a peeled hard-boiled egg (or 2)
a couple of small ice cubes
a glass tomato puree bottle, glass milk bottle or other glass bottle with an opening slightly smaller than the egg
an adult weilding a match
The Wind Above My Wings
- Hold two adjacent corners of a sheet of notebook paper in front of your face. Now blow across the top of the paper. What happens?
Not So Light Reading
Gravity, weight and air pressure:
- Place two rulers on the table so that the ends extend off the edge and they are about 1/4 of the way from either edge.
- Spread the newspaper on the table over the rulers and flatten it with your hands so that it lies flat on the table and ruler with no bumps or creases sticking up.
- Without tilting the rulers, and keeping them even with each other, try and lift them straight up. What happens? Why do you think that is?
Full of Hot Air
Air temperature, pressure and volume:
- Blow up both of your balloons so that they are the same size as each other.
- Measure their circumferences and record your measurements.
- Place one in a warm area (a patch of sunlight will do) and the other in the freezer.
- Check the balloons in about an hour. What do you notice? What happens if you leave them for longer?
Go Suck an Egg
Air pressure vs. a vacuum:
- Sit your boiled egg in the mouth of your bottle to ensure it doesn't fall through.
- Now, tear a small strip of paper from your notebook sheet and stuff it into the bottom of the bottle. Have your adult light a match and drop it into the bottle. As soon as the paper catches fire, place the egg on the top of the opening. What happens?
- Carefully shake out the bits of paper, then tilt the bottle upside down and blow into the bottle past the egg to release it again (Drat! I gave it away!)
- From what you've learned about air pressure, can you explain what happens with the egg in this demonstration?
- Now, try the same thing again (if your egg deformed you may need to use a second boiled egg this time), but this time, instead of using the paper and a flame, insert a couple of ice cubes into the bottle before placing the egg in the mouth of the bottle. What do you think will happen? Why? Were you right?
How Wings Really Create Lift
Many people believe that when air passes over a wing section, the air that passes over the top moves faster to meet the air from the bottom at the end of the wing, thereby creating lower air pressure along the top of the surface. This video demonstration from New Scientist Magazine uses puffs of smoke over an airfoil to show that that isn't quite how it works in reality.