Free Body Diagrams & Equilibrium — Lesson 3

This lesson covers the concept of equilibrium, particularly in static systems. It explains the definition of equilibrium as per Newton's laws of motion, stating that a body at rest or in a state of uniform motion remains unchanged unless an external force acts upon it. The lesson further elaborates on how to quantify equilibrium in static systems, emphasizing that the summation of all forces acting on a body must be zero for the body to be in equilibrium. The lesson also discusses the concept of moments and their role in determining equilibrium for finite-sized bodies. For instance, a body is in equilibrium when both the summation of forces and the summation of moments are zero.

Video Highlights

00:00 - Introduction to the problem of a block on an inclined plane
02:00 - Explanation of a free body diagram
06:01 - Calculation of forces required for equilibrium
09:07 - Application of the two laws of equilibrium
19:18 - Differentiation between forces caused by constraints and forces controlled to maintain equilibrium

Key Takeaways

- A free body diagram is a graphical illustration used to visualize the forces acting on a body.
- Equilibrium occurs when the sum of all forces and moments acting on a body is zero.
- A rigid body is a body in which the distance between any two points remains constant regardless of external forces.
- Forces can originate from two different physical processes: an external agent applying force and a constraint causing force.
- In a free body diagram, the action of external agents on a body can be replaced with forces.
- The principles of equilibrium can be used to calculate the forces required to keep a body in equilibrium.