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
can you find out using an Air Track?
You can find out:
Is a force
really needed to keep an object moving?
What would it be
like in space (where there is no
friction) if two objects collided?
continued presence of a force keep an object
moving at a constant speed?
What forces are
experienced in collisions and why
should we wear seat belts?
How can I build my own air
track and save $$$?
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
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
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!
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
Use a 1mm or
less drill bit to make holes about
1cm apart along two faces of the downpipe (see Fig 1).
nozzle from a vacuum cleaner into the
partially open end of your air track, blow in some air, watch your car
Things to try:
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
13 Physics students Reece Munro and
Brendan Wakeman test the air track and sensor system they have
were awarded First Prize in the Senior
Technology section of the 2003 Fonterra Taranaki Science &
The lead to
the SuperMouse is on the table.
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
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
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.
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!
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.
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
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.