Nano PHYSICS . MECHANICS . DYNAMICS . FORCES AND INTERACTIONS

Force Diagrams vs Free-Body Diagrams

Use an interaction diagram to show what is interacting in a scene, then use a free-body diagram to isolate the forces acting on one chosen object or system.

Physics · Mechanics · Dynamics · Forces and Interactions · Force Diagrams vs Free-Body Diagrams
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: two diagram styles, two purposes
Free
Distinguish a scene-level interaction diagram from a free-body diagram that isolates one chosen object or system.
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Goal: know which diagram communicates interactions in a scene and which diagram supports force analysis of one system.
STEP 2
Conceptual grounding: from interaction map to free-body diagram
Free
Practice translating an interaction partner list into justified force arrows on one isolated object.
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Goal: use an interaction diagram as a source-checking step before building a free-body diagram.
STEP 3
Real-world connection: choose the diagram that fits the task
Free
Compare common mechanics scenes and decide whether you need an interaction map, a free-body diagram, or both.
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Goal: recognize when a scene is complex enough that an interaction diagram prevents missing or inventing forces.
STEP 4
Check your understanding: diagram-choice mini-quiz
Paid
Attempt each question before revealing the reasoning about interaction sources, force arrows, and isolated systems.
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Goal: select the correct diagram style and identify what belongs in each representation.
STEP 5
Practice: build interaction maps and free-body diagrams
Paid
Work through increasingly rich scenes by identifying interactions first and then isolating the force arrows on a chosen object.
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Goal: build a dependable two-stage routine for force analysis: interaction map first, free-body diagram second.
STEP 6
Summary & reflection + diagram-switch explorations
Paid
Consolidate the two diagram styles and explore how a force model changes when the chosen object or system changes.
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🔒 ▶ Explore interactive simulation
Goal: build the lasting habit of checking force sources with an interaction diagram before relying on a free-body diagram.