Experiment with Gears
Gears can help us do work by speeding up or changing the direction of motion. To see how this works, make a model set of gears!
What You Need:
What You Do:
- Print out the pattern for the gears and color them however you like. You can cut them out if you want, or just tape the whole paper to the Styrofoam tray.
- Have an adult cut the Styrofoam around the pattern to make Styrofoam gears. (The easiest way to do this is to cut out a circle along the outside edge of the teeth, then make the cuts around the teeth.)
- Once you have your gears cut out, use thumbtacks to pin them to a piece of cardboard or another tray. Pin them so that their teeth fit together.
- If you want to, you can make a small turning handle on the big gear by taping a little piece of Styrofoam so it stands straight up on the gear.
You've just built a gear train. The big gear is the driver. Try turning it slowly. What happens to the little gear? Which way does it turn? Draw a big colorful dot on each gear, and position the gears so that both dots are at the top. As you turn the big gear, have one person count how many times the big gear turns all the way around and another person count how many times the small gear does. Do they turn the same number of times?
Gears work to change the direction of motion. When you turned the big gear one way, the little gear turned the other way! Gears also change speed of motion. When you turn the big gear slowly, the smaller gear turns faster. This helps save energy, because you don't have to work as hard to turn the big one slowly as if you had to turn the small one quickly.
You can also try this project with water bottle caps that have ridges, or with gears from a building set like Lego or K'Nex.
See How a Screw Works
An inclined plane, such as a ramp, is a kind of simple machine that helps do work. A screw, just like the ones from a hardware store, is also a simple machine! A screw is made from an inclined plane being wrapped around and around. To see how this works, you will need notebook paper, and a pencil or marker.
- Cut 2.5 inches off a piece of printer paper to make a square.
- Fold the top corner over until it meets the opposite bottom corner - you've now made a triangle! The long edge looks like an inclined plane, although the paper is too thin to do any real work.
- Starting from one of the short sides of the triangle, wrap the paper once around the pencil or marker, then start rolling until the whole piece of paper is wrapped around the maker.
- Put a finger on the end of paper to keep it from unrolling, and carefully pick up the screw you have made. Do you see how the long edge of the triangle is now traveling around and up the marker? This is just like the inclined plane wrapped on a screw!
Because of the inclined plane, screws can hold all sorts of things together. If you like, try making different shapes and sizes of triangles, and wrap them around a marker or pencil to make different kinds of screws.