Cue Column:

• Steps to draw FBD?
• Common mistakes?
• Which forces to include?

Notes:

Step-by-step FBD construction:

1. Isolate the body from its surroundings
2. Draw the body as a point or simple shape
3. Identify and draw ALL forces acting ON the body:
   • Weight (mg) — always vertically downward
   • Normal (N) — perpendicular to contact surface
   • Tension (T) — along string, away from body
   • Friction (f) — along surface, opposing relative motion
   • Applied forces — as specified
4. Choose coordinate axes (along and perpendicular to motion or incline)
5. Resolve forces along chosen axes
6. Apply $F_{net}$ = ma along each axis

Common FBD errors:

• Including forces BY the body (action-reaction confusion)
• Missing normal force or friction
• Wrong direction of friction
• Including "ma" as a force (it's the RESULT, not a force)
• Not resolving forces along inclines

Summary: FBD is the single most important skill in mechanics. Master it.