Nano PHYSICS . MECHANICS . MOMENTUM AND COLLISIONS . SYSTEM BOUNDARIES AND EXTERNAL FORCES

Identifying System Boundaries

The system is what you choose to analyze. The boundary determines what counts as external, so system choice is the most important step in momentum-conservation problems.

Physics · Mechanics · Momentum and Collisions · System Boundaries and External Forces · Identifying System Boundaries
Access for this nano-lesson
Unsigned visitors can show & copy prompts for Steps 1-3. Signed-in free accounts can also Run with AI for Steps 1-2. Paid accounts unlock everything (Steps 1-6 + Help prompts + AI).
Steps 1-3 Free Steps 4-6 Paid
STEP 1
Orient: identifying system boundaries
Free
Establish system boundaries as the key to internal and external force classification.
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Goal: define system boundaries and explain why they control what counts as external.
STEP 2
Conceptual grounding: build the system-boundary model
Free
Build a workflow for systems, interaction intervals, internal forces, external impulses, and conservation decisions.
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Goal: classify forces and impulses as internal or external for a chosen system.
STEP 3
Real-world connection: interpret internal and external effects
Free
Apply boundary reasoning to collisions, push-offs, walls, Earth interactions, friction, and external pushes.
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Goal: explain internal cancellation, external momentum change, short-time approximations, and non-conservation cases.
STEP 4
Check your understanding: diagnostic mini-quiz
Paid
Attempt each question before revealing the system-boundary reasoning.
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Goal: identify and correct boundary, internal-force, external-impulse, and short-time errors before they become calculation errors.
STEP 5
Practice: solve increasingly rich boundary and impulse situations
Paid
Apply the model to situations that grow in complexity.
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Goal: write concise, physically justified system-boundary and external-impulse explanations.
STEP 6
Summary & reflection + explorations
Paid
Consolidate the model and explore changing system boundaries, external impulses, and conservation conclusions.
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🔒 ▶ Explore interactive simulation
Goal: carry the model forward into momentum conservation, collisions, explosions, recoil, and rocket-style systems.