For children in Grade 4 learning about structures and mechanisms.
From the Curriculum:
Students will learn that pulleys and gears can transfer motion from one object to another, transform one kind of motion into another, change the speed and direction of an object’s motion, and change the amount of force needed to move an object. They will identify how these devices are used to improve everyday life, learn about mechanical advantage, and apply what they have learned through investigations of their own design.
Pulleys and gears change the speed, direction, and motion of, and force exerted on, moving objects.
Pulleys and gears make it possible for a small input force to generate a large output force. (Note: Grade 4 students need to understand mechanical advantage only in its qualitative sense).
Gears are specialized wheels and axles that are used daily in many machines.