Here’s a great activity to do at home and sneak in some cool science. You can build a 2- wheel balloon car and use your breath to power it! Try your hand at engineering design and learn about a simple machine (wheel and axle); explore the physics of motion; and experience potential and kinetic energy with this fun DIY activity inspired by PBS KIDS Design Squad.
Things to think about and discuss before you get started:
What types of fuel are used to power cars and airplanes? Can you name some? (Some cars use gasoline, diesel fuel, solar power and even electricity to charge batteries. What type of fuel do Rockets and Jets use? Can you think of any other types of fuel that make things move?) In this project, you will use your BREATH for fuel to power your homemade racer.
What’s the Science?
Your breath, a balloon and a straw will create air pressure that will power your racer across the table. When you blow up the balloon and set your racer down and let it go, escaping air from the balloon rushes out of the straw. This is your car’s PROPULSION SYSTEM. The stored air in the balloon pushes through the straw, creating thrust – the force that pushes the car forward. When air from the balloon moves in one direction, it pushes the car in the opposite direction.
The principle at work here is Newton’s Third Law of Motion:
SIR ISAAC NEWTON was an English scientist who lived from 1642 to 1727. Newton is best known for 3 very important principles of physics called classical mechanics. These principles describe how things move and are referred to today by his name – Newton’s Laws of Motion. There are 3 of them. This activity illustrates, NEWTON'S THIRD LAW of MOTION, “For every action there is an equal and opposite reaction.” SIMPLY MEANING, if you push an object, that object pushes back in the opposite direction equally hard. In the case of the balloon-powered car, the balloon squeezes air out in one direction, creating thrust that forces the car to go in the opposite direction. For more on Newton’s Third Law of Motion go to Physics 4 Kids.
You are also fueling your racer with POTENTIAL ENERGY. The POTENTIAL ENERGY of the car is stored in the expanding elastic material of the balloon. As the balloon fills with air, it adds more potential or stored energy. As the air flows from the balloon, the energy changes to KINETIC ENERGY or the energy of motion. The moving balloon-powered car is using Kinetic Energy and keeps going until there’s not enough energy to move it anymore.
What are the 6 types of simple machines?
- Wheel and axle (you’ll explore in this activity)
- Inclined plane
Explore the Engineering Design process as you troubleshoot and refine your car design for optimum efficiency.
Here’s what you need to make your 2-Wheel Balloon Car:
- 1 balloon (9-inch or smaller)
- 1 flexible straw
- 1 straight paper straw – cut in half
- 1 wooden tongue depressor or craft stick
- 2 round candy mints (with a hole in the center)
- Duct tape
How to Make It:
To encourage your child to do more of the decision making in the engineering design process, leave off some of the details and let them learn by trial and error. Try building it different ways and see what works best.
STEP 1: Make the JET
This is your propulsion mechanism. Hold the flexible straw with the flexible end up. Slide balloon over the top of the straw above the flexible bend. Stop when you get to where the straw flexes. (What would happen if you used the other end of the straw?)
STEP 2: Making the JET continued
Using duct tape, wrap the base of the balloon with a few tight spiral wraps. Be sure tape sticks to both the balloon and the straw. Blow into the straw to test for leaks. Add more tape if needed.
STEP 3: Attach the JET to the BODY of Your Car
Tape the JET to the top of the craft stick (i.e. the body). Make sure the jet is as parallel to the floor or tabletop as possible. If it points up, down, or to the side, your car won’t move as fast or far as if the jet points straight back. (What happens if your balloon points down? What happens if your balloon hangs off the end of the body?)
STEP 4: Make the AXLE and WHEELS
Slip two candy mints onto the half of a paper straw. Bend back the tips of the straw so the candy can’t fall off. Tape the tips in place if needed.
STEP 5: Attach AXLE and WHEELS to Car Body
Tape the axle to the bottom of the body, at the front- the balloon end. Make sure the wheels spin freely. Make sure the wheels line up with the direction you want the car to move. (What happens if they are crooked?)
STEP 6: Power Your Car!
Blow up the balloon. Put your finger over the end of the straw to stop air from escaping. Make sure the balloon doesn’t flop over onto the tabletop. If it does, it will act like an anchor and will stop the car from moving. Put the car on a smooth surface. Let go of the straw. ZOOM!
More THINGS to TRY!
- Go for the record. How far can your car go? Try to double the distance by reducing friction (rubbing); making the car lighter, pointing the jet back straighter and straightening the axle.
- Decorate and have a parade. Give your cars personalities by decorating them. Have a parade to show off all the balloon cars.
- Try making a 4 -wheel balloon car or try making your car out of other materials. Which one goes straighter? Faster?
- Change the size of the wheels to determine how that might affect the distance and direction your car travels.
- Test different sizes of the straws – the jet and the axle- to see what happens.
For more engineering projects for kids check out PBS KIDS Design Squad. And be sure to try out their “Stuff Spinner” to make things out of stuff you have around the house!