LEVER SYSTEMS & FREE BODY DIAGRAMS

Lesson 6

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 Rotational Motion

- Displacement - Angular displacement

- Velocity - Angular velocity- Acceleration - Angular

acceleration- Force - Torque- Mass - 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 ContinuedLinear Motion: Acceleration: Force

MassRotational 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, actingalone or in combination with others, is part of alever 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 loadExample – the neck moving from a

position of flexion to extension

Lever Systems

Class 2 Lever: (Wheelbarrow) The resistance is between the force

and the fulcrumExample – 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 bodyExample – 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 interest2) Draw all external forces acting on the body3) Label the center of mass and base of support4) Identify and fully label the lever systems in

use5) Show direction of motion for the major limbs

in useWebsite 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!