After learning the basics of the scientific world in grade school, middle school students start applying physical sciences in their own creative, ingenious ways. Project inspirations that get students inventing and perfecting mechanical structures give kids a means of exploring their own interest in engineering while learning about the scientific principles involved in their creations. Start with some classic invention ideas that give students a chance to apply their own knowledge and insight to basic problems.

Catapult

For this invention, give each student the same requirements in terms of the object to be fired and some of the parameters of the catapult itself. For safety and the best chances of effectiveness, use a light object like an egg, small rubber ball or ping-pong ball. Some parameters and limitations for the catapult itself include limits on the use of electricity or gas, limits to the height and weight of the finished machine and which kinds of materials are allowable for construction.

Egg Drop

For this classic invention project, instruct students to create a protective structure designed to keep an unboiled egg from cracking and breaking when dropped from height. As with the catapult project, give the students limitations in terms of the size of the protective apparatus to keep them thinking about effectiveness of structure rather than substituting quantity of padding and insulation for quality. Do not, however, limit the materials students can use to encourage them to explore the protective properties of different substances and craft materials.

Balloon Popper

Use this invention project to give students a chance to explore mechanical structures and their cause-and-effect relationship. Instruct students to design a mechanical device for popping balloons that uses a clockwork structure with a complex system of interacting parts. Since this is not a strictly necessary or useful invention, designs should emphasize creativity of structure and smoothness of operating mechanisms, with refinement of motion being key.

Moving Toy Car

For this invention, students should create a means of powering a toy car, whether it's through the potential energy of wound rubber bands, electric motors or sails. Test the vehicles according to how far they can run, testing like vehicles (in terms of how they're powered) against like vehicles for the sake of fairness.

Insect Trap

For this project, instruct students to come up with an innovative means of capturing and trapping household insects. Guide them to form their inventions based on reading about the behavioral patterns of various insects. Give them examples of successful inventions, such as roach "motel" traps, fly paper and fruit fly traps made from funnels inside large jars.