Lecture Notes: Free Body Diagrams and Resultant Forces

Introduction to Free Body Diagrams

• Definition: Simple diagrams showing all forces acting on an object.
• Representation: Use force arrows to illustrate forces.

Example: Plane Flying Through the Sky

• Forces Illustrated:
  • Thrust: Forward arrow.
  • Air Resistance (Drag): Backward arrow.
  • Weight: Downward arrow.
  • Lift: Upward arrow.

Characteristics of Forces as Vectors

• Components:
  • Magnitude: Indicated by the length of the arrows.
  • Direction: Indicated by the direction the arrows point.
• Labeling: Forces are labeled in Newtons for precision.

Resultant Force

• Concept: Overall force on an object after accounting for all acting forces.
• Method: Consider horizontal and vertical directions separately.

Example Calculations

1. Vertical Component:

   • Forces: 80,000 N up and 80,000 N down.
   • Resultant: 0 N (forces cancel out).

2. Horizontal Component:

   • Forces: 120,000 N right and 90,000 N left.
   • Calculation: 120,000 N - 90,000 N = 30,000 N.
   • Resultant: 30,000 N to the right.

Scenario Variation

• Change in Air Resistance:
  • Example: Air resistance is 120,000 N.
  • Resultant Force: 0 N (balanced forces).
  • State: Object is in equilibrium; no net force.

Conclusion

• Key Takeaway: Free body diagrams help us visualize and calculate the resultant force by considering all acting forces and their components separately.
• Application: Useful for understanding force balance and equilibrium.

These notes summarize the concepts and calculations related to free body diagrams and how they determine the resultant force on an object.