1. Introduction to Statics
Discussion topics:
Newton’s 3 laws of motion
Translational equilibrium
Rotational equilibrium
Scalars/vectors

2. Free Body Diagrams
Statics
Principles of EngineeringTM
Unit 4 – Lesson Statics
The analysis of loads (force, torque, moments) on systems in a state of rest or uniform motion (i.e. constant velocity)

3. Initially, at least, this is a statics problem

4. Newton’s 3 Laws of Motion

5. Free Body Diagrams
Statics Principles
Principles of EngineeringTM
Unit 4 – Lesson Statics
Newton’s First Law of Motion (law of inertia): An object in a state of rest or uniform motion (constant velocity) will continue to be so unless acted upon by an unbalanced external force.

6. Free Body Diagrams
Statics Principles
Principles of EngineeringTM
Unit 4 – Lesson Statics
Newton’s Second Law of Motion: The acceleration of an object is proportional to the net force acting on the object and inversely proportional to the object’s mass Force = Mass x Acceleration

7. Free Body Diagrams
Statics Principles
Principles of EngineeringTM
Unit 4 – Lesson Statics
Newton’s Third Law of Motion: (law of interaction) For every action force, there is an equal and opposite reaction force

9. Equilibrium Static Equilibrium:
Free Body Diagrams
Equilibrium
Principles of EngineeringTM
Unit 4 – Lesson Statics
Static Equilibrium:
A condition where the external forces acting on a body are balanced. The body remains at rest or continues at a constant velocity

10. Free Body Diagrams
Equilibrium
Principles of EngineeringTM
Unit 4 – Lesson Statics
Translational Equilibrium: The state in which the vector sum of all forces = 0. The body remains at rest, or continues moving at constant velocity.

11. Equilibrium Rotational Equilibrium:
Free Body Diagrams
Equilibrium
Principles of EngineeringTM
Unit 4 – Lesson Statics
Rotational Equilibrium:
The state in which the sum of all the torques = 0. The system does not rotate. Clockwise moments = counterclockwise moments about a pivot point.
Remember
M = d x F

12. Statics Principles
Free Body Diagrams
Principles of EngineeringTM
Unit 4 – Lesson Statics
Scalar Quantities: A physical quantity that has magnitude only
©iStockphoto.com
©iStockphoto.com

13. Free Body Diagrams
Statics Principles
Principles of EngineeringTM
Unit 4 – Lesson Statics
Vector Quantities: A physical quantity that has both a magnitude and direction

14. Forces illustrated, or “Why we follow safety rules and wear protective gear”

15. What Is a Force? The pushing or pulling interaction of objects
Free Body Diagrams
What Is a Force?
Principles of EngineeringTM
Unit 4 – Lesson Statics
The pushing or pulling interaction of objects
A vector quantity defined by its known magnitude, direction A
45 lbf
21.8°NE

16. Force Units U.S. System (U.S. Customary Units)
Free Body Diagrams
Force Units
Principles of EngineeringTM
Unit 4 – Lesson Statics
U.S. System (U.S. Customary Units)
pound (lb), sometimes called pounds-force (lbf)
Metric System (S.I. Units)
newton (N)
Conversions between Unit Systems
1lb = N
1N = lb

17. Static Equilibrium Force Principles
Free Body Diagrams
Principles of EngineeringTM
Unit 4 – Lesson Statics
Static Equilibrium Force Principles
Forces always occur in pairs acting on two different objects. (Newton’s 3rd law). Force pairs act in opposite directions and have the same magnitude.

18. Force Components
Free Body Diagrams
Principles of EngineeringTM
Unit 4 – Lesson Statics
A single force can be replaced by component forces if their combination produces the same effect as the original force. a Fa
Fay
Fax a

19. Free Body Diagrams
Resultant Force
Principles of EngineeringTM
Unit 4 – Lesson Statics
A single force that has the same effect as two or more concurrent forces
7lbf
Resultant force =
2lbf
5lbf
3lbf
Resultant force
5lbf
2lbf =