CHAPTER 4 AN INTRODUCTION TO BIOMECHANICS. Biomechanics Biomechanics is the study of how and why the...
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Transcript of CHAPTER 4 AN INTRODUCTION TO BIOMECHANICS. Biomechanics Biomechanics is the study of how and why the...
CHAPTER 4CHAPTER 4
AN INTRODUCTION TO AN INTRODUCTION TO BIOMECHANICSBIOMECHANICS
BiomechanicsBiomechanics Biomechanics is the study of how and why Biomechanics is the study of how and why
the human body moves. the human body moves. It investigates how the physical laws of It investigates how the physical laws of
mechanics apply to the human body.mechanics apply to the human body. Role of biomechanist: Role of biomechanist: analyse an athletes analyse an athletes
performance in order to improve performance in order to improve technique, improve equipment design and technique, improve equipment design and reduce injuries.reduce injuries.– Quantitative Analysis:Quantitative Analysis: use of numbers (eg use of numbers (eg
speed / distance / time)speed / distance / time)– Qualitative Analysis: Qualitative Analysis: description without description without
numbers (eg bend your kneesnumbers (eg bend your knees Checkpoints: Checkpoints: Page 95 – Q.1,3 Page 95 – Q.1,3
Principles of BiomechanicsPrinciples of Biomechanics CD-ROM:CD-ROM:
– OverviewOverview– InertiaInertia– Mass Mass – ForceForce
Types of forcesTypes of forces
– Newtons Laws of MotionNewtons Laws of Motion Velocity: (page 98)Velocity: (page 98)
– What does velocity measure?What does velocity measure?– What are its two important characteristics?What are its two important characteristics?
Read: Reality PE Snapshots (Page 99)Read: Reality PE Snapshots (Page 99)– Radar equipment!Radar equipment!
Principles (cont)Principles (cont) CD-ROM:CD-ROM:
– ImpulseImpulse Checkpoints: Checkpoints: (page 102)(page 102)
– Questions: 1, 2, 4, 5Questions: 1, 2, 4, 5 Acceleration: (Newton’s 2Acceleration: (Newton’s 2ndnd law) law)
– What is acceleration?What is acceleration?– How do you calculate acceleration?How do you calculate acceleration?
Conservation of momentum: (Newtons 3Conservation of momentum: (Newtons 3rdrd law) law)– What is this principle?What is this principle?– Give an example of how this principle works?Give an example of how this principle works?
Elasticity:Elasticity:– What does the term elasticity mean? Explain two ways in What does the term elasticity mean? Explain two ways in
which a tennis player can generate more velocity which a tennis player can generate more velocity through elasticity.through elasticity.
Principles (cont)Principles (cont) Summation of Momentum:Summation of Momentum:
– Define summation of momentum?Define summation of momentum?– When does effective summation of When does effective summation of
momentum take place?momentum take place? CD-ROM:CD-ROM:
– FrictionFriction Checkpoints: Checkpoints: (page 112)(page 112)
– Questions 3, 5, 6Questions 3, 5, 6
Balance and StabilityBalance and Stability Read pages 113-118Read pages 113-118 Define the terms Balance and Stability?Define the terms Balance and Stability? What factors affect balance and stability?What factors affect balance and stability? Explain the difference between static and Explain the difference between static and
dynamic balances?dynamic balances? What is meant by the ‘centre of gravity’ and What is meant by the ‘centre of gravity’ and
how does it change when you change your how does it change when you change your body position?body position?
How does the mass of a person affect their How does the mass of a person affect their stability?stability?
CD-ROM: CD-ROM: Recap of balance using CD Recap of balance using CD examples.examples.
Basic movement patternsBasic movement patterns
Striking Throwing
StoppingRunning
Basic movement patternsBasic movement patterns
StrikingStriking ThrowingThrowing RunningRunning StoppingStopping
TennisTennisGolfGolfVolleybalVolleyballlllCricketCricket
BaseballBaseballBasketbaBasketballllNetballNetballAthleticsAthletics
AthleticAthleticssBasebalBaseballlCricketCricketSoccerSoccer
BaseballBaseballNetballNetballAthleticsAthleticsCyclingCycling
Biomechanical principles associated Biomechanical principles associated with basic movement patternswith basic movement patterns
Striking - Striking - GolfGolf
Throwing - Throwing - BaseballBaseball
Running - Running - AthleticsAthletics
Stopping - Stopping - NetballNetball
Newtons Newtons laws (force)laws (force)leversleversmomentummomentumimpactimpactstabilitystability
projectile projectile motionmotionflattening flattening the arcthe arcsummation summation of of momentummomentumaccuracyaccuracy
forces forces (action/ (action/ reaction)reaction)motion motion (straight (straight line)line)momentumomentummfrictionfriction
forcesforcesacceleratioacceleration and n and decelerationdecelerationNewtons Newtons lawslawsfrictionfriction
Tennis
Biomechanical principles Biomechanical principles associated with tennisassociated with tennis
ForcesForces LeversLevers TorqueTorque VelocityVelocity PowerPower AccelerationAcceleration DecelerationDeceleration Projectile motionProjectile motion MomentumMomentum ElasticityElasticity
Coefficient of restitutionCoefficient of restitution
SpinSpin Centre of gravityCentre of gravity Base of supportBase of support AccuracyAccuracy MassMass InertiaInertia MotionMotion ImpulseImpulse
TennisTennis
Force (Newtons N)Force (Newtons N)– A push or a pullA push or a pull– What effect does a force have on an What effect does a force have on an
object?object?
Starts, stops, speeds up, slows Starts, stops, speeds up, slows down, down, changes direction. It changes changes direction. It changes an objects velocityan objects velocity
Velocity (msVelocity (ms-1-1))– displacement / timedisplacement / time
Mass (kg)Mass (kg)– Amount of matter in an objectAmount of matter in an object– Weight is an indirect measure of massWeight is an indirect measure of mass
Acceleration (msAcceleration (ms-2-2))
- change in velocity / time- change in velocity / time
- - final velocity – initial velocityfinal velocity – initial velocity
timetime
Newtons lawsNewtons laws
1.1. A body continues in its state of rest A body continues in its state of rest or of or of uniform motion in a straight line uniform motion in a straight line unless it is unless it is compelled to change that compelled to change that state by forces state by forces acting on it.acting on it.
2.2. The acceleration of an object is The acceleration of an object is directly directly proportional to the net force proportional to the net force applied and applied and inversely proportional to its inversely proportional to its mass.mass.
F = maF = ma3.3. For every action the is an equal and For every action the is an equal and
oppositeopposite reaction.reaction.
MomentumMomentum
Momentum (kg msMomentum (kg ms-1)-1)
- p = mv - p = mv - two objects travelling at the same - two objects travelling at the same velocity, the one with the greater velocity, the one with the greater mass will have the greater momentum mass will have the greater momentum and vice versa, two objects of the and vice versa, two objects of the same mass, the one travelling at a same mass, the one travelling at a greater velocity will have a greater greater velocity will have a greater momentum.momentum.- momentum is always conserved- momentum is always conserved
Impulse Impulse – Change in momentumChange in momentum– I = I = p OR I = Ft p OR I = Ft – Impulse can be increased by increasing Impulse can be increased by increasing
the force applied or increasing the time the force applied or increasing the time over which the force is applied.over which the force is applied.
– When a mass is constant, a change in When a mass is constant, a change in impulse will result in a greater release impulse will result in a greater release velocity of the object (ball)velocity of the object (ball)
Summation of momentumSummation of momentum– Used to maximise the speed of the Used to maximise the speed of the
racquet headracquet head– Works when the larger slower body Works when the larger slower body
parts begin the movement and move parts begin the movement and move sequentially through until the smaller sequentially through until the smaller and quicker finish the movement.and quicker finish the movement.
– See laboratorySee laboratory
ElasticityElasticity– The ability of an object to return to its The ability of an object to return to its
original shapeoriginal shape– The more quickly an object does this the The more quickly an object does this the
less energy it loosesless energy it looses– Coefficient of restitution is a measure of Coefficient of restitution is a measure of
an objects elasticityan objects elasticity
e = e = height bouncedheight bounced
height droppedheight dropped– String tension determines how much String tension determines how much
contact time the ball has with the contact time the ball has with the racquetracquet
LeversLevers– Classes of leversClasses of levers– Factors that affect the use of external Factors that affect the use of external
leverslevers Length of leversLength of levers Inertia of the leverInertia of the lever ForceForce
Compare and contrast techniques Compare and contrast techniques (elite and novice)(elite and novice)
Evaluate performance using Evaluate performance using biomechanical principlesbiomechanical principles