Lesson 6

LEVER SYSTEMS & FREE BODY DIAGRAMS

Quote of the day...

“It is the mark of an educated mind to be able to entertain a thought without accepting it.”

- Aristotle

General Feedback From Phase 1

 Questions & Concerns:  The use of class time  Problems with technology  Formatting / Independent study skills  Things Done Well  Anatomical terms and descriptive detail

Phase 1 Feedback

 Areas for Improvement  Repetition of similar observations  Avoid using LEFT & RIGHT terminology  Dominant hand + Non-dominant hand  Lead foot + Trail foot  Weight bearing leg + Non-weight bearing leg  Front foot + Back foot  What to look for? Where do I find it?

 P. 231 – First 3 Principles of Biomechanical Analysis

Review Key Concepts

1.

What are Newton’s Three Laws of Motion? 2.

What are the different types of motion?

3.

Linear & Rotational Motion Terminology

Key Terms Linear Motion

- Displacement - Velocity - Acceleration - Force - Mass

Rotational Motion

- Angular displacement - Angular velocity - Angular acceleration - Torque - Moment of inertia

Moment of Inertia

Recall the relationship between Mass, Force and Acceleration...

 The moment of inertia describes the distribution of mass in relation to it’s distance from the axis of rotation  The further the mass is from the axis of rotation, the greater the moment of inertia (therefore the harder it is to cause it to spin or stop it from spinning)  The closer the mass is to the axis of rotation, the easier it is to rotate it or stop it from rotating

Moment of Inertia Continued

Linear Motion: Acceleration: Force Mass Rotational Motion: Moment of Acceleration: Torque Moment of Inertia  Key Idea: The larger the moment of inertia, the more difficult it is to change the state of motion of that object.

Small Moment of Inertia Large Moment of Inertia

Lever Systems

Every moveable bone in the human body, acting alone or in combination with others, is part of a lever system that facilitates movement.

Components of Lever Systems

: 1) Fulcrum (axis) – the pivot about which a lever turns 2) Load (resistance) – the amount of weight placed on a lever system 3) Force (muscle) – the pull acting in opposition of the load

Lever Systems

Class 1 Lever: (Teeter-totter)  The fulcrum is located between the force and the load Example – the neck moving from a position of flexion to extension

Lever Systems

Class 2 Lever: (Wheelbarrow)  The resistance is between the force and the fulcrum Example – the ankle joint. The gastrocnemius muscle pulls on the calcaneus to plantar flex the foot  Second class levers can lift the largest amount of weight

Lever Systems

Class 3 Lever: (Snow Shovelling)  The force is between the fulcrum and the resistance  The most common lever system in the human body Example – the bicep-elbow complex  With this lever system there is a speed/muscle trade-off

Activity:  Handout - Labelling Lever systems:

Free Body Diagrams

Simplified representations of the body, and forces acting upon it

Construct a Free Body Diagram :

1) Isolate the body or interest 2) Draw all external forces acting on the body 3) Label the center of mass and base of support 4) Identify and fully label the lever systems in use 5) Show direction of motion for the major limbs in use Website practice http://www.physicsclassroom.com/class/newtlaws/u2l2c.cfm

Homework

 Review Phase 1 of your sport skills analysis:    For each phase, assess where the fulcrum, load and force are located.

What type of lever system is causing movement?

Come to LAB tomorrow with Phase 1 and homework questions completed ASK QUESTIONS DURING CLASS TIME!