This unit focuses on familiarizing students with basic engineering knowledge related to simple mechanical and electrical systems and the use of mathematical models to represent design ideas and to inform design decisions. Students begin by reverse engineering a mechanical device to identify simple machines and mechanisms that influence motion and contribute to the function of the device. Students identify different types of motion (rotary, oscillating, linear, and reciprocating) and investigate mechanisms that cause motion (including cams, gears, pulleys, chain and sprockets) and later use these mechanisms to create, transform, and control motion to solve a problem. Students practice CAD skills by developing assembly models of the mechanisms they investigate and simulating motion in the CAD environment. To support efficient CAD modeling, students will also learn to use mathematical functions to represent dimensional relationships in a 3D solid model.  Students  investigate forces that resist motion. First students study spring forces and develop a mathematical model to determine the relationship between spring displacement and force for a given spring. Students also learn about simple electrical circuits and how to transform electrical power to motion using a motor. Students design and install a circuit to run a hobby motor that powers their previously designed automaton. As part of the electrical circuit, students develop a mathematical model to inform the design of a simple potentiometer to control the speed of the motor.  As an end of course project, students design and build a toy that includes an electro-mechanical system that will produce realistic motion of a figure(s) or object(s) resulting from the rotation of an axle powered by a motor with minimal frictional resistance.  As part of the automaton design process, each student creates a CAD assembly model and creates a computer simulation of automata motion, CAD technical drawings, and a physical working model of their design.