Balloon-Powered Car

Let's Try It

1. 

   Use the ruler to measure two, 3” (8 cm) pieces from one of the straws. Grab the scissors and cut the two pieces from the straw. These pieces will hold the axles of your car.

2. 

   You have some choices to use for the frame or base of your car. One is very rigid cardboard that holds its shape well. Another is called foam core. It’s also rigid and light weight. It’s available in most school or business aisles of grocery stores and pharmacies as well as at any business supply store. It’s a foam material sandwiched between very stiff paper. It’s not too expensive and you’ll need only a single piece. It comes in colors, too, so be choosy.

   Cut out your base material so that it measures about 3 x 6” (7.5 x 15 cm).

   Securely tape the two straws you just cut to the underside of the base. Since they hold the axles, the straws need to be as parallel to each other and as perpendicular to the centerline of the base as possible.

3. 

   Almost all balloons have a mouthpiece on them that you blow through to inflate them. Use the scissors to trim this ring off of the balloon. The goal is to insure a tight seal to the straw in the next Step.

4. 

   Slide the straw into the balloon about 2” (5 cm) and use tape to make it an airtight connection. The tape needs to touch both the balloon and the straw for a couple of tight, spiral wraps.

5. 

   Turn the base so the straws are on the bottom and decide which end will be the front and which will be the rear of your car. You want to place the straw toward the rear of the car and the balloon toward the front in about the center of the base. The straw sticks way out of the back and it needs to be as straight as you can make it. Securely tape the straw in place over the tape already on it from Step 4.

6. 

   From the flat end (not the pointy end) of the skewer, measure two 4” (10 cm) lengths. With the scissors or a small saw, cut the measured lengths. These are the axles for your car. Save the pointy end for the next Step. Slide the new axles into the straws on the base.

7. 

   Use the soda bottle cap to trace four circles on the cardboard. These will be the wheels for your car so draw them carefully. Use the ruler to draw two diameters on each wheel. You need to know where to find the center of each. Cutting out the wheels is as important as having parallel axles so take your time. Use the best tool you have to make them the same size and as evenly round as you can.

   Use the pointy end of the skewer to poke a small hole through the very center of each wheel. That would be where the two diameter lines cross.

8. 

   Attach the perfectly round wheels to the perfectly parallel axles through the perfectly centered holes. Keep the wheels perfectly parallel to and aligned perfectly with each other, too. Perfect! OK, that was a little much but the alliteration was fun. Just do your best and enjoy yourself as well.

   This is the power moment! Go to your preferred track location (any hard surface works) and fuel your racer with potential energy by inflating the balloon. Block or pinch the straw as you set up on the start point and then release it when you’re ready to roll. Potential energy converts to kinetic energy, Newton’s Third Law of Motion kicks in, and your racer screams down the track!