How to Build a Car Using Newton's Third Law
A toy called "Newton's car" is propelled by the principle behind Newton's third law of motion, also called the "law of interaction." It states that for each action, there is an equal and opposite reaction. This means that an object pushed off the car pushes back on the car with the same force, propelling the car forward.
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Things You'll Need
- Inflexible straws or round pencils
- Rubber band
- String
- Block of wood, about 5 by 10 by 1 inches
- Wood plane
- Matches or scissors
- Plastic photo film container
- 3 wood screws or nails
- Screwdriver or hammer
- Coins or lead shot
Instructions
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1
Use the plane to shave the front lower edge of the wood block (the 5-inch edge), to reduce friction when the car runs on a track. The track will be made of the pencils or straws, which will roll under the wood block.
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2
Drill or hammer two of the screws or nails into the back of the car. They will stand vertically at the two corners.
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3
Drill or hammer the third nail or screw at the front of the car, centered between the two corners.
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4
Wrap the rubber band around the two back screws/nails, and draw it toward the front of the car. It will make a V shape.
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5
Connect the rubber band to the front screw/nail with a loop of string.
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6
Position a film container, weighted with coins, lead shot or the like, at the bottom of the V shape formed by the rubber band.
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7
Lay out the straws/pencils in parallel, each in front of the other, to form a track for the car to roll on. Place the car on the track lengthwise.
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8
To release the rubber band, and launch the container, sever the string either by burning it or cutting it. The container will launch off the back. The car pushes on the container as much as the container pushes on the car, so the car launches forward.
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