Free body diagrams and vectors

Free body diagram

Isolated drawing of an object that is assumed to be rigid

* observational tool

Benefits of free body diagrams

* less distractions
* Can focus on critical joint movement and posture
* Rigid segments where forces act

Limitations of FBD

* lose context - rotation
* Perspective
* Depth
* Range of motion
* Subjectivity (of choosing joint centres)

Vector

* arrow connecting two points
* Direction
* Magnitude
* Point of application

What can vectors represent

* forces
* Motion
* Displacement (vs distance which is scalar)

A vector can be ___ __into__ _____

Broken down

Components

Adding vectors

* add tip to tail - then draw resultant tail to tip
* Break down into components and add those to determine resultant

Force

A push or pull