Compound machines are any combination of simple machines used to reduce the amount of work necessary to perform an action. Simple machines include gears, inclined planes, levers, screws, pulleys, wedges and wheels and axles. Compound machines can be any combination of two or more of these simple machines, including two of the same machine. Fifth grade science projects that involve compound machines help students learn about the prevalence and importance of simple machines in daily life, as well as deepen their understanding of basic physics principles and the function of simple machines.
Compound machines can be demonstrated and turned into projects by using simple machine kits. Since compound machines are made up of two or more simple machines, students can experiment with constructing compound machines out of any combination of simple machine kits. For instance, students can test whether a simple machine of a pulley or a compound machine of several pulleys strung together is more effective for lifting the same amount of weight. Similar experiments can also be done with different combinations of simple machines and meters, measuring the joules of work done to perform an action.
Simple compound machines can also be created out of various household objects. For instance, a compound machine used for scooping can be made out of a dustpan and a stick of wood or a broomstick. Attach the wood to the dustpan with tape and you have a lever with an inclined plane for scooping up any number of small items. Additionally, you can create an axle and pulley system out of paper plates by joining them together with a pencil. Wrap string around the pencil then pull it to unravel it. The string functions as a pulley which puts the wheel and axle in motion.
Fifth grade science students can also create a science project by identifying all of the compound machines they use or see daily. For instance, can openers use a gear to move the blade, which is itself a wheel, along the can. A bicycle is also a compound machine that uses gears which move a chain. The chain, in turn, moves the tires to create motion, and the tires themselves are simple machines made of wheels and axles. Students should try to find a compound machine that uses at least one of each simple machine and illustrate the way these compound machines work.