Make cardboard gears. You will need the following materials: Cardboard - it can be thick or thin cardboard
Pen
Compass (if available)
Scissors strong enough to cut the cardboard
Five to eight round items of different sizes to use to trace circles. (One should be quite small, such as a spice bottle or small glass jar. One should quite large, such as a large cooking pan. The others should range in size between these two extremes)

STEPS FOR MAKING GEARS

diagram A for making gears

a. Trace the circumference of the large pan on the cardboard and cut it out. Label this “Gear A.” Mark the exact center of the gear and cut a small hole in the exact center. Now find a pan that is a little smaller (one to two inches smaller in diameter) and trace its circumference onto Gear A (be sure to line the smaller pan up so that it is centered on Gear A). See diagram A.

diagram B for making gears

b. Now mark every 1/2 inch along the inner circle. Every other 1/2 inch mark should be heavy - alternate light lines and heavy lines. It will be faster if, each time you make a mark, you use a ruler that goes through the center of the gear and you mark the other side as well. See diagram B.

Diagram C for making gears

c. Place your ruler through the middle of Gear A and line it up on one of the light 1/2 inch marks. Put a mark where your ruler intersects the outer circle. Do this for each of the light 1/2 marks that you made on the inner circle. See diagram C.

Diagram D for making gears

d. Now draw 1 inch lines around the outer rim of Gear A, using each 1/2 inch mark as the center point for the 1 inch line. See diagram D.

e. You are almost done! Now cut your gears out as shown in diagram D.

f. Make two more gears (one small and one medium) in the same way. Be sure to always use 1/2 inch increments. The medium gear should be labeled Gear B and the small one labeled Gear C.
Now you are ready to use your gears. Download the Gear Chart worksheet and complete as you do the following activities.

a. Put a stick or pencil through the center of each gear. Try putting them together, two at a time, by fitting the notches of one into the notches of the other. Use the small one to turn the big one. Use the big one to turn the medium one. Use the medium one to turn the big one and then the small one.

b. Download and print the chart below, fill it by using your gears. Make a red mark on the rim of each of your gears. Fit Gear A into Gear B at the point at which the two red marks touch. Turn Gear A one full turn; how many turns does Gear B make? Is it fewer than Gear A or is it more than Gear A? Fill in the chart accordingly. For example, if for every turn that Gear A makes, Gear B turns 3 times, write “3” on the chart and fill in the ratio as 1:3. (The ratio is however many times the second gear turns in respect to one turn of the first gear.)

Turn in your completed Gear Chart to your teacher here.