How to Make a Compound Machine for a 3rd Grade Science Project

By Etch Tabor

Nearly every tool we use in our daily lives is a compound machine. A compound machine is merely a combination of two or more simple machines. The simple machines are the lever, the wedge, the wheel and axle and the incline plane. In some instances, the pulley and screw are also referred to as simple machines. Although creating a fairly complex compound machine might be a task for an older student, a third grader can create a very basic compound machine with just two or three simple machines.

Toy Scooper

Place the dust pan near one end of the broom handle so that the handle of the dust pan and the handle of the broom are parallel and touching.

Affix the dust pan to the handle with rubber bands.

Use the tool to scoop up items on the ground such as small toys. The broom handle acts as a lever while the dust pan acts as both an incline plane and a wedge. This simple device is made of three simple machines.

Big Wheels

Glue two paper plates together so that the two tops of the plates are facing each other. Do this for two sets of plates.

Take a pencil and stick it through centers of both sets of plates. Your project should look like two large wheels with the pencil serving as an axle.

Wrap a piece of string around the pencil but leave enough thread so you can grip the string.

Pull the string to unravel the thread from around the pencil. Your pencil will begin to turn which will cause the plates to turn, moving your machine forward. The plates and pencil act as a wheel and axle while the string and pencil act as a pulley, making a compound machine.

About the Author

For three years, Etch Tabor worked as the technology and online editor at "InsideCounsel" magazine, a national publication for in-house counsel. He currently is a full-time freelance writer, specializing in legal, technology and comedy writing. He graduated in 2004 from the University of Missouri-Columbia with a degree in journalism.