Teknologi Hijau - Akademi Sains Malaysia

Objective
Investig
you build ate
esfi , m 3
as
an air Ne-tipooVeredhvehicle.
What You Need
• Half-Gallon Milk Carton
• Balloon
• 2 Drinking Straws
Spools
• 4 Straight Pins (length
shorter than sp
• Sharp Scissors
• Ruler
• Pen
To Do and Observe
h must be
1 Wash out your carton and cut off the top. The
milk carton will be the body of your vehicle.
/Cut carton into half the long way.
3.Cut a small hole in the middle of one of the
short sides of the carton. This hole should be
the same diameter as the neck of the balloon.
Start with a small hole. The fit must be precise
if the hole is too big or too small, the flow of
air won't create enough force to move the car.
4.Pull the end of the balloon through the hole,
keeping the body of the balloon inside the carton.
If the neck of the balloon is squeezed, enlarge
the hole. Repeat until the fit is snug, but
not tight. Air flow should not be restricted.
5.Mark the spots on the sides of the carton
where you will cut holes for the axels. Use a
ruler to make sure the holes on opposite sides
of the carton will match up. Use the spools to
measure and make sure the axel holes are at
a height that will allow the spool-wheels to
touch the rolling surface and lift the body off
the surface.
C.Cut holes for axels and push straws through
the holes.
.Slide spools on to the straws and poke pins
through the straws to keep the spools on. Adjust
the pins as needed until the wheels spin
freely.
NOTE: For younger children, please
have a parent or other adult to help in
this step.
8.Finally, blow up the balloon - don't tie the end
- and let your car go.
What's Going On
This activity allows you
to explore a range of science
topics including Newton's
Third Law, simple machines
and friction. Newton's Third
Law states that for every action
there is an equal and opposite
reaction. If you let go
of a balloon filled with air,
what happens? The balloon
flies around somewhat randomly
as the air escapes. As
the balloon contracts it forces
the air out of its opening. Air has mass, it is made
of molecules. The air molecules that are pushed
out of the balloon push against the molecules in
the atmosphere creating a reaction force called
thrust that acts on the balloon. Thrust acts on the
balloon with equal force in the opposite direction
as the air that is squeezed out. In this activity,
because the balloon is attached to the vehicle,
the balloon stays put, but thrust causes the car
to move.
Without the spools on the balloon car, do you
think the car would move? It probably would, but
not as far. That is because much more of the bottom
surface of the car would make contact with
the surface that it is moving on. This increased
amount of contact would lead to lots of friction,
the force of two surfaces in rubbing against each
other. By adding the spools to the car, we decrease
the amount of friction because only the spools
-acting as wheels-are making contact with the
surface, and they are spinning rather than rubbing.
The wheel and axle are one of the six types of simple
machines, which are tools that allow us to do a
certain amount of work (like used air to push a car
a certain distance) by
than would be needed
without the simple
machine. We find
examples of simple
machines around us
all the time. Some
examples of a wheel
and axle that help
us every day are
doorknobs and the
gears in a clock.
Can you think of
some others?
Parent/Teacher Tips
For Older Children
applying a smaller force
For Younger Children
Before the children attach
the wheels and axles, have
them blow up the balloons
and let their cars go. How far
does the car travel? Does it go
very fast? Have the children
hypothesize as to what modications
might make the car
travel farther and faster?
Have the children test their balloon cars on different
surfaces. Ask them to observe or measure how far and
how fast the car travels on a carpet. Then have the children
do the same thing on a smooth, flat table. Were
there any differences in the car's speed or distance traveled
on the different surfaces? On the textured surface
of the carpet there will be more friction and the balloon
car should not be able to travel as fast or as far as it will
on a smooth surface. The children can make hypotheses
about additional types of surfaces and other variables,
perform tests and observe the results.