Build an Air Track! An air track is a device that can provide a (near) frictionless surface on which to investigate how objects move. Jets of air forced out of holes along the tracks length can allow a "car" or "glider" to float above its surface. Some High School physics labs have an air track. They usually cost over $500 and can be attached to a computer to record data and graph results.

What can you find out using an Air Track?

You can find out:

How can I build my own air track and save $$$?

For those of us with little or no money to spend on the commercially available air track kits, here is a simple and effective home made air track made from some scrap plastic downpipe... it took me five minutes with nothing more than an idea in my head...

Fig. 1. End on view of car (A) & air track (B)	Cut a length of plastic down pipe, 1m - 2 m long, depending on what kind of experiments you want to do. Block off one open end completely using an end cap or just use some tape. The other end will be partially blocked leaving an opening just big enough for a vacuum cleaner nozzle to fit in snugly. I used masking tape for my prototype. The idea is then to drill holes along two surfaces of the downpipe (B) so that when tilted at 45 degrees the car (A) will float on a cushion of air from both sides of the track.
Fig. 2. The "car" (A) and air track (B)	Cut a "car" (A) from an off-cut of downpipe. The length is not really important, try 10 cm to begin with. Cut the sides of the car so that the car will trap enough air underneath it when placed on the track. You can see that this end of the air track has an opening for the vacuum cleaner nozzle...you could do a much neater job but I was rushed!
Fig. 3. Drilling the holes	From figure 1 above you want the jets of air to strike the car about 1/3 of the way up from the bottom edge of the car. Use a pencil to score a line along the downpipe on the two faces you will drill. Use a 1mm or less drill bit to make holes about 1cm apart along two faces of the downpipe (see Fig 1). Push the nozzle from a vacuum cleaner into the partially open end of your air track, blow in some air, watch your car float!

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Things to try:

Make many more cars. On some you can attach magnets using BluTack or a hot glue gun. Get one car moving (say towards the right) and collide it with another car (either sitting in the middle of the track stationary, or coming from the other end moving left).

A PRIZE WINNING PROJECT! Year 13 Physics students Reece Munro and Brendan Wakeman test the air track and sensor system they have assembled. They were awarded First Prize in the Senior Technology section of the 2003 Fonterra Taranaki Science & Technology Fair. The lead to the SuperMouse is on the table.

Here are some example collision combinations you could try; make up more of your own experiments and see what you can discover about acceleration, forces, momentum and kinetic energy...

CAR 1	CAR 2
Expt 1: normal mass (moving right)	double mass (stationary)
Expt 2: double mass (moving right)	normal mass (stationary)
Expt 3: normal mass North magnet (moving right)	normal mass (North magnet, stationary)
Expt 4: normal mass North magnet (moving right)	normal mass North magnet (moving left)
Expt 5: normal mass South magnet (moving right)	?????

 See the video here: http://www.youtube.com/watch?v=0tzFyXWFg_w

Some points to note:

1. Remember that your vacuum cleaner will only supply a fixed amount of air each second. Therefore the air pressure coming out of the air track jets will only lift a car up to a maximum weight - important if you intend adding magnets or other data logging aids.

2. The closer you drill the holes, the less air pressure each will provide since there are more holes in total along the entire length of the track from which air can escape. This also puts limits on the maximum length of track you can successfully use. If your car won't hover, use tape to block off any unwanted holes until the remaining holes have enough air pressure to provide lift.

3. The bigger the jet holes the less pressure each will provide. Use a drill bit no bigger than 1mm in diameter. Take care when drilling not to break the bit!

4. If you make a mess of things, just tape over the holes you drilled and flip the downpipe over and use the remaining two sides to drill a new set of holes.

5. You might decide to cut your cars to a shorter length in order to reduce weight. This may allow you to create a longer track even though it provides less air pressure overall. BUT remember that your car must trap air from a certain number of jets in order to hover...if you cut the car too short it will no longer get enough lift!

6. You can easily make a stand that allows you to adjust the angle of the air track and keep it level. Go ahead and figure out the best set up for your home/garage/classroom.

7. You can use a sensor system like our SuperMouse datalogger to record data!

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