Free-body diagrams

Science

Definition

A simplified drawing that shows all the forces acting on a single object as arrows. Each arrow represents a force, with its length indicating magnitude and its direction showing where the force acts. They are essential for solving problems using Newton's laws.

How It Works

  1. Identify the object of interest and isolate it
  2. Draw the object as a simple shape (dot or box)
  3. Identify all forces acting ON the object (gravity, normal, friction, tension, applied)
  4. Draw each force as an arrow starting from the object, pointing in the correct direction
  5. Label each force with its name or symbol
  6. Use the diagram to set up Newton's second law equations (ΣF = ma)

Examples

  • A book on a table with gravity pulling down and the normal force pushing up
  • A box being pushed across a floor showing applied force, friction, gravity, and normal force
  • A hanging sign with tension forces in the cables and gravity pulling down

Related Terms

Newton's three laws Net force Friction Acceleration

Study This Concept

Practice free-body diagrams with free review games in these units:

AP Physics 1 Unit 2: Forces and Newton's Laws Physics Unit 2: Forces and Newton's Laws