When you tape the balloon to a straw and attach it to the body of your car, however, you can control the direction of the escaping air. When the end of the straw is aimed backward, the air pushes your car forward, as described by Newton's third law of motion. Your design will be most efficient if the straw is pointed straight back and not downward or to the side.
The more you inflate the balloon the more potential energy it stores, which in turn is converted to more kinetic energy, according to the law of conservation of energy—so the car will go faster. You may find your car does not work perfectly on the first try, particularly if its axles are not parallel or the wheels wobble. Too much friction can cause the wheels to get stuck, and the balloon will not be powerful enough to push the car forward.
Test your car to make sure the wheels spin freely and, when you give it a push, the car rolls easily. If not, you might need to make some adjustments to your design. You should also make sure no air escapes the balloon where it is taped to the straw, and re-tape it more tightly if necessary. This activity brought to you in partnership with Science Buddies. Follow him on Twitter BenFinio. Already a subscriber? Sign in. Thanks for reading Scientific American.
Create your free account or Sign in to continue. See Subscription Options. Discover World-Changing Science. Key concepts Physics Kinetic energy Potential energy Conservation of energy Newton's laws of motion Introduction Turn a pile of trash into a toy car—and watch it go!
Materials Plastic bottle Four plastic bottle caps Wooden skewer Two straws Balloon Tape Scissors or sharp knife Have an adult use or supervise your use of this tool. In kicking a football, the foot pushes on the ball and the ball pushes on the foot in the opposite direction with the same amount of force. Aboriginal and Torres Strait Islander people are advised that the Questacon website may contain images of people who have passed away. Questacon is reopening on 19 November!
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Balloons are elastic and store potential energy when they are filled with air. When the air is released, the potential energy is converted into the energy of motion, which is also known as kinetic energy. This is the energy you see when the car is propelled forward. The more potential energy is stored, the more kinetic energy the car will have when you let it go!
Observe and describe the conversion of energy from potential to kinetic energy. Per Class: masking tape hammer nail. Per Student: 1 tongue depressor 2 short pieces of straws cut the width of the tongue depressor 1 straw 2 bamboo skewers 4 plastic pop bottle lids 1 balloon. What happens when you blow the balloon bigger? Keep in mind how the size may affect how far the car will go.
Each team should select an individual in charge of blowing up their balloon. Note: Blow the balloon up a couple times to stretch it out.
Assemble the Chassis and Suspension: a. Cut the straw into two pieces. The length should be equal to the width of the water bottle. Tape the two straw pieces underneath the water bottle where you feel the front and rear wheels should go.
Keep the straws lined up so the car travels in a straight line. Cut two pieces of the wooden skewer. The length should be between an inch to an inch and a half longer than the straw that was taped to the bottle. Put one end of each wooden skewer through your wheel. If the wheel is loose on the skewer use modeling clay to hold in place.
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