This resource is explicitly designed to build towards this performance expectation.
Comments about Including the Performance Expectation
In this activity, students are using, not developing, a model to investigate the role of gravity within a system. Although the activity limits itself to investigating the actions of orbiting spacecraft, the same scientific principles apply to the motions of moons, planets and even solar systems in the universe. Prior to the lesson, teachers should introduce the concepts of gravity and velocity (and how it differs from speed). Since the activity concerns itself with calculating escape velocities, teachers will need to emphasize that escape velocity is a function of both gravity and velocity. For example, teachers should check to see that students understand which part(s) of the model represents these two forces. Students should recognize that the spinning actions represent velocity; however, students may have difficulty relating the twine/clothespin apparatus to gravity.