Gears operate simple and complex machines that make work easier, leaving complicated tasks for a machine to complete. A lesson on how gears work and which machines use them is fun for kids of all ages. Students will have the chance to understand how machines work and to recognize everyday items that use gears. Incorporating information on gears with hands-on activities provides a strong basis toward understand how a simple machine works.

Gears Definition

Gears are a very simple machine that makes work easier on humans and motors. A gear is a version of the wheel and axle. An axle is an object inserted into the middle of the wheel, which also connects to a machine. A gear is a wheel with teeth, which enables the gear to mesh with another gear, creating movement and rotation.

Pre- and Post-Activity Discussion

Before doing an activity with gears, explain that motors alone do not create an effective machine. A motor supplies speed for the parts within a machine, but a motor lacks the torque, or force, to make the parts move. Gears supply torque to the motor, allowing the motor to use the parts effectively. Encourage the children to ask questions about how gears work so they fully understand before proceeding to the activities. Once the students have completed the activities, ask them what they learned from the lesson. Ask them to write a few ideas that they learned and to then share their ideas with another child. For homework, ask the children to find three items around the house that use gears.


Supply the students with plastic gears. A 3/16-inch screw inserted into the middle of the gears doubles as an axle. Drill holes into small pieces of plywood, so the screws fit into the drilled holes. Alternatively, you can cut out gears from cardboard and use a round-head paper fastener as an axle. Attach the gears to another piece of cardboard by using the axle of the paper fastener. Ask the children to color one tooth black on each gear. For each gear they use in the activity, record the number of teeth. While rotating the gears, record how many times the driver gear and the driven gear rotate. The children will be able to form turn-to-turn ratios for the gears used. Ask the children to experiment with the number of gears used. They should notice how many times each gear turns and the direction of each gear.

Gears in Machines

Many machines use gears to run effectively. It is easy for you to supply the students with a list of items that use gears. For the children to learn best, however, you must ask them to provide you a list of items that use gears. You can start off with a few items such as a crane, bicycle, electric drill, car, clock and robot. Ask them to make a list of five items that use gears. Go over the items by asking where the gears are located within the machine and what each gear's purpose is within the machine.