# Motion and Stability: Forces and Interactions

## Performance Expectations

PS2 support students’ understanding of ideas related to why some objects will keep moving, why objects fall to the ground and why some materials are attracted to each other while others are not. Students should be able to answer the question, “How can one explain and predict interactions between objects and within systems of objects?” The disciplinary core idea expressed in the Framework for PS2 is broken down into the sub ideas of Forces and Motion and Types of Interactions. The performance expectations in PS2 focus on students building understanding of forces and interactions and Newton’s Second Law. Students also develop understanding that the total momentum of a system of objects is conserved when there is no net force on the system. Students are able to use Newton’s Law of Gravitation and Coulomb’s Law to describe and predict the gravitational and electrostatic forces between objects. Students are able to apply scientific and engineering ideas to design, evaluate, and refine a device that minimizes the force on a macroscopic object during a collision. The crosscutting concepts of patterns, cause and effect, systems and system models, and structure and function are called out as organizing concepts for these disciplinary core ideas. In the PS2 performance expectations, students are expected to demonstrate proficiency in planning and conducting investigations, analyzing data and using math to support claims, applying scientific ideas to solve design problems, and communicating scientific and technical information; and to use these practices to demonstrate understanding of the core ideas.

## Calculation Method for DCI

Disciplinary Core Ideas are larger groups of related Performance Expectations. So the Disciplinary Core Idea Grade is a calculation of all the related Performance Expectations. So click on the Performance Expectation name below each Disciplinary Core Idea to access the learning targets and proficiency scales for each Disciplinary Core Idea's related Performance Expectations.