ME 201 Engineering Mechanics: Statics Chapter 3 – Part b - continued 3.1 Condition for the Equilibrium of a Particle 3.2 The Free-Body Diagram 3.3 Co-Planar Force Systems

Key Concepts  Problem Solving Methodologies

Steps to Problem Solving 1.Draw a Free Body Diagram (FBD), label known and unknowns  Simple sketch of isolated particle  Sketch all forces that act on the particle  Active forces  Reactive forces  Label known forces with proper magnitude & direction  Watch signs – negative means opposite sense from as drawn in FBD 2.Apply equations of equilibrium  Any suitable direction  2 equations, 2 unknowns (n equations, n unknowns)

Solving Spring Problems  Typically 3 components (in addition to FBD): Equations of Equilibrium Spring Equation Geometry

Free Body Diagram In Class Exercise  Determine the stretch in each spring for equilibrium of the 2 kg block. The springs are shown in the equilibrium position.

Solving Multiple Freebody Diagram Problems  Sketch possible FBDs  Select FBD with fewer unknowns to begin  Transfer results from first FBD to second FBD

Free Body Diagram In Class Exercise  Determine the force in each cable and the force F needed to hold the 4 kg lamp in the position shown.