HS-PS2-2

Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.

Clarification statement: Emphasis is on the quantitative conservation of momentum in interactions and the qualitative meaning of this principle.

Assessment boundary: Assessment is limited to systems of two macroscopic bodies moving in one dimension.

Performance Level Descriptions

Every Regents exam question on HS-PS2-2 is written to match one of the performance level descriptions (PLDs) below.

Level 1: Given data and/or a model, use a mathematical representation for momentum to identify the mass, or the momentum (with or without direction), or the velocity/speed of an object.

Level 2: Given data and/or a model, use a mathematical representation to determine the total momentum, with or without direction, of a system of objects before or after an interaction when there is no net force on the system.

Level 3: Given data and/or a model, use a mathematical representation for the conservation of momentum to determine the mass and/or velocity of an object before or after an interaction between two objects when there is no net force on the system.

Level 4: Use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.

Level 5: Collect and analyze data and use mathematical representations to support the claim that the total momentum of a system of objects is conserved when there is no net force on the system.

Resources

Examples and discussion of resources for the learning, teaching, and assessment of HS-PS2-2.

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Regents Exam Questions

Released New York State Regents exam questions that assess HS-PS2-2 are listed here by exam and question cluster. Each link opens the question with its answer key.

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NGSS Dimensions

Performance expectation HS-PS2-2 was developed using the following elements from the NRC document A Framework for K-12 Science Education:

Science and Engineering Practices

• Using Mathematics and Computational Thinking
  • Use mathematical representations of phenomena to describe explanations.

Disciplinary Core Ideas

• PS2.A: Forces and Motion
  • Momentum is defined for a particular frame of reference; it is the mass times the velocity of the object.
  • If a system interacts with objects outside itself, the total momentum of the system can change; however, any such change is balanced by changes in the momentum of objects outside the system.

Crosscutting Concepts

• Systems and System Models
  • When investigating or describing a system, the boundaries and initial conditions of the system need to be defined.

Page contributors: Caroline Leonard, Conrad Richman

Physics | HS. Forces and Interactions