Forging new generations of engineers Free Body Diagrams

Forging new generations of engineers

Free Body Diagrams A lesson on creating force diagrams

In This Lesson: What are free body diagrams, and how are they used? What are the types of forces? How do we create free body diagrams? How do free body diagrams apply to pulley systems? How do free body diagrams apply to trusses?

What is a Free Body Diagram?

Newton’s Third Law For every action, there is an equal and opposite reaction. THE TOP ROCK PUSHES DOWN ON THE BOTTOM ROCK PUSHES BACK UPWARD ON THE TOP ROCK

What is a Force? A push or a pull acting on an object as the result of an interaction with another object.

Types of Forces Applied force: one object acts on another Wind pushing on the boat Fapp

Types of Forces Tension force: transmitted through string, cable, wire, rope, or chain the n o lling u p e Rop boat θ F tens

Types of Forces Gravity force: weight; the mass of the Earth pulling on the mass of the boat W Gravity pulling the mass of the boat down

Types of Forces Normal force: support force Water pushing back up on the boat FN

Types of Forces Friction force: opposes the motion of the object Water pulling on boat Ff

What is a Free Body? Substitute a simple shape for the object being analyzed. Fapp F tens Ff FN W

Creating the Free Body Diagram

Creating the Free Body Diagram Ftens θ θ Ff FN W

Creating the Free Body Diagram F app Ff W FN W θ θ Ff FN

Creating the Free Body Diagram Ftens Fapp θ θ WSIGN WELCOME Fapp WSIGN

Your Turn to Create a Free Body Diagram SICS PHY E TUR ITEC H ARC

Your Turn to Create a Free Body Diagram FN SICS PHY HITE RE CTU ARC FN Fapp θ Fapp W W FN θ FN

A Different Method FN SICS PHY RE CTU HITE ARC FN Fapp FN θ Fapp W W FN θ

Pulley Systems Ftens FBD of M 1: M 2 FBD of the movable pulley: WM 1 Ftens WM 2 M 1 Tension Forces (Ftens ) are equal throughout the system.

Trusses B A C L D

Trusses B FAX A C FAY L D FDY

Trusses B FAB FBC FAX A FAC FAY C L FBD FCD D FDY

Trusses B FAB FFBDAB FBC FAX A FAC FAY C L FAC FAY CD NODE A D FDY

Trusses B FAB FBD FBC FAX A FAC C FAB FAY FBC L NODE B FCD D FBD FDY

Trusses NODE C B FBC FCD FAC FAB FBC FAC C L FBD L FCD D FDY

Trusses FBD B FBC FBD FCD C FCD D FDY NODE D L FDY

B Trusses FAB FAX A FAC FAY FBC FBD FBC FCD FAC C FCD FDY D L

References Department of Physics, University of Guelph (n. d. ). Free body diagrams. Retrieved January 29, 2008, from http: //eta. physics. uoguelph. ca/tutorials/fbd/Q. fbd. html Garrett, J. (1999). Truss analysis methods. Retrieved March 2, 2008, from http: //www. ce. cmu. edu/~garrett/courses/12 -100/LECTURES/trussanalysis-ho. pdf Vawter, R. (2007). Free-body force diagrams. Retrieved March 6, 2008, from http: //www. ac. wwu. edu/~vawter/Physics. Net/Topics/Dynamics/Forces/Free Body. Diagram. html

Credits: Writer: Wendy De. Mane Content Editor: Production Work: