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Free-Body Diagram Tutorial

Run the Free-Body Diagram Tutorial Fullscreen

About This MicroSim

This interactive tutorial teaches students how to draw and interpret free-body diagrams (FBDs), the essential tool for analyzing forces in physics. The simulation presents four scenarios of increasing complexity:

  1. Book on Table - Static equilibrium with balanced weight and normal force
  2. Book Pushed with Friction - Net force causing acceleration with applied force and friction
  3. Box on Inclined Plane - Force decomposition with tilted coordinate systems
  4. Elevator Accelerating Upward - Apparent weight changes with non-zero acceleration

Features

  • Proportional Arrows Toggle - Switch between force arrows scaled to magnitude or uniform length
  • Show Calculations - Display the mathematical analysis for each scenario
  • Tips Panel - Quick reference for FBD drawing conventions
  • Visual Comparison - See both the physical situation and abstract FBD side by side

Learning Objectives

After using this simulation, students will be able to:

  • Identify all forces acting on an object in various scenarios
  • Represent objects as points in free-body diagrams
  • Draw force vectors with appropriate directions and labels
  • Decompose forces into components for inclined plane problems
  • Calculate net force and predict acceleration from FBDs
  • Understand the relationship between net force and equilibrium

Lesson Plan

Introduction (5 minutes)

  • Explain that FBDs are the foundation of force analysis
  • Review that forces are vectors with magnitude and direction

Guided Exploration (15 minutes)

  1. Start with Scenario 1 (Book on Table) - static equilibrium
  2. Toggle "Proportional Arrows" to see that balanced forces have equal magnitudes
  3. Progress through each scenario, discussing what forces are present
  4. For Scenario 3, discuss why we tilt the coordinate system

Practice Questions

  1. Why doesn't the book in Scenario 1 accelerate even though gravity pulls on it?
  2. In Scenario 2, which direction does the net force point? How do you know?
  3. Why is the normal force in Scenario 3 less than the weight?
  4. In Scenario 4, if the elevator were accelerating downward, would the scale read more or less than 686 N?

Common Mistakes to Avoid

  • Including velocity or acceleration arrows on FBDs (only forces!)
  • Forgetting to include all forces (especially normal force)
  • Drawing forces acting on different objects in the same diagram
  • Confusing weight and mass