#### Sketcher Basics

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Transcript Sketcher Basics

ME 201
Engineering Mechanics: Statics
Chapter 3 – Part A
3.1 Condition for the Equilibrium of a Particle
3.2 The Free-Body Diagram
3.3 Co-Planar Force Systems
Key Concepts
Equilibrium of a Particle
Free Body Diagrams
Problem Solving Methodologies
Equilibrium of a Particle
A particle is in equilibrium provided it is at rest if
originally at rest, or has a constant velocity if
originally in motion
Static equilibrium
Object at rest
Then to satisfy Newton’s first law, the resultant
force acting on a particle is zero, or
F 0
Equilibrium of a Particle
In vector notation:
∑ Fxi + ∑ Fyj = 0
Or, for this equation to be satisfied
∑ Fx = 0
∑ Fy = 0
Free Body Diagrams
A Free Body diagram is a simple sketch of
the particle (or member), including all forces
that act on the particle (or member)
Creating a Free Body Diagram
Sketch the isolated particle (or member…)
Sketch all forces that act on the particle
Active forces
Reactive forces
Label known forces proper magnitude & direction
Watch signs
Negative answer means opposite in sense from FBD
Free Body Diagram
Example
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
2.
Active forces
Reactive forces
Label known forces with proper magnitude & direction
Watch signs – negative means opposite sense from as drawn in
FBD
Apply equations of equilibrium
Any suitable direction
2 equations, 2 unknowns (n equations, n unknowns)