Download - Biomechanics 1
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Synovial joint structure - knee
Femur
Tibia
Patella
Tendon
Cruciate ligaments
Articular cartilage
Synovial fluid within synovial cavity
Bursa
Bursa
Meniscus
Pad of fat Ligament
Joint capsule
Quadriceps
Synovial membrane
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Structure of a synovial joint
Features that improve STABILITY
Features that improve MOBILITY
Ligament
Meniscus
Joint capsule
Articular cartilage
Synovial fluid
Bursa
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STRUCTURE & FUNCTIONAL CHARACTERISTICS OF SYNOVIAL JOINT
Joint feature Structure Function
Joint Capsule
Discs of fibro-cartilage
Synovial fluid
Synovial membrane
Articular cartilage
Bursa
Ligaments
Pads of fat
Meniscus
Fibrous tissue encasing the joint Forming a capsule around the joint adds stability
C-shaped rims of fibrocartilage Acts as shock absorbers
A fluid that fills the joint capsuleNourishes and lubricates the articular cartilage
Lines the joint capsule Secretes synovial fluid
Covers the articulating surfaces of the bones
Prevents friction between the ends of bones
White fibrous connective tissue which attaches bone to bone
By securing the bones of joints together it adds significantly to joint stability
A sac filled with synovial fluid located between tendons/ligaments and bones
To reduce friction where tendons, ligaments, muscle or bones might rub together
Fatty tissue located between fibrous capsule and bone or muscle
Provides a cushion between the joint capsule and the bone/muscle
Wedges of fibrocartilage found between bones
Stabilises joint by improving the fit between bones. Reduces wear & tear
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Anatomy and Physiology 5
Motion and movement 1
Biomechanics:
Newton’s Laws of Motion
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SPORTS BIOMECHANICS
Biomechanics is the study of body movements and of the forces acting on the musculoskeletal system
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Specification
Candidates should be able to:
Define Newton’s law of motion
Describe the types of motion produced (linear, angular or general)
Describe the effect of force, direction of the force and the position of application of force on a body
Define centre of mass
Explain the effect of changes on the position of the centre of mass and the area of support when applied to practical techniques
Carry out practical analysis of typical physical actions
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Learning Objectives
To know and understand Newton’s three laws of motion The types of movement that can be produced
Be able to Apply the laws of motion to explain the type of
movement produced Describe the effect of force in sporting actions
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Types of motion
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Linear motion
When a body moves in a straight or curved line with all it’s parts moving in the same
direction and at the same speed.
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Angular motion
When a body or part of a body moves in a circle or part of a circle about a particular point called the axis of
rotation
Movement occurs around a fixed point or axis (including around the joints of the body)
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So what type of motion is this?
Consider…….
1. Flight of javelin
2. Run up
• Javelin
• Torso
• Leg action
• Arm action
Linear motion
Linear motion
Linear motion
Angular motion
• Upper legs rotate about shoulder joints
• Lower legs around the knee joint
• Feet around the ankle joints
Angular motion
• Non-throwing arm rotates about shoulder joint
GENERAL
MOTION
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General motion
A combination of linear and general motion
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Identify the types of motion
5
3
4
2
1
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Task
Write a definition ofLinear motionAngular motion General motion
Give at least one sporting example for each of these types of motion and explain why it is that type of motion
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Force
A push or a pull that alters the state of motion of a body
What can a force do to an object?
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Effects of force
A force can cause… A body at rest to move A moving body to change direction A moving body to accelerate A moving body the decelerate A body to change its shape
Give a relevant sporting example for each of these effects
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Effects of force
What factors affect the extent of these effects?
Size of the force (how many Newtons)Application of forceDirection of the force
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Motion and movement
Sir Isaac Newton
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Video – Newton’s 3 laws of motion
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Newton’s 1st law of motion
A body will continue in a state of rest or uniform velocity unless acted
upon by an external force
Inertia = resistance of a body to change its state of motion
“Law of Inertia”
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Newton’s 2nd law of motion
“When a force acts on an object, the rate of change of momentum experienced by the object is proportional to the size of the force and takes
place in the direction in which the force acts”
Law of Acceleration
F = ma
F is the applied force
m is the mass of the body/object
a is the acceleration of the body/object
‘The acceleration of an object is directly proportional to the force causing it and is inversely proportional to the mass
of the objects’
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Newton’s 2nd law of motion
How is velocity different to speed?
• Both are the distance covered per second
• But velocity is a vector quantity and hence has direction as well
as size
What is Acceleration?
• The rate of change of velocity
• Acceleration = change in velocity/time
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Newton’s 2nd law
What is momentum? Momentum = mass x velocity
= mv
2nd law
F = ma
F is the force applied, m is the mass of the object and a is the acceleration
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Newton’s 2nd law of motion
When a force acts on an object, the rate of change of momentum experienced by the object is proportional to the size of the force and takes
place in the direction in which the force acts
“Law of Acceleration”
The acceleration of an object is directly proportional to the force causing it and is
inversely proportional to the mass of the objects
F = ma
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Newton’s 3rd law
For every action there is an equal and opposite reaction
When a body exerts a force on another body then there is an equal and opposite force exerted back
Action Reaction
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Law’s of motion
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Law’s of motion
Ensure that you have a definition of each of the 3 laws of motion
Ensure that you also know them by their alternative names (e.g. Law of Inertia)
Apply each of Newton’s 3 laws of motion to
1) A penalty kick2) Another sporting action of your choice
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Laws of Motion
http://www.youtube.com/watch?v=UVdqxYyFRKY
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Generating motion
How can you produce linear motion?
A force is applied through the centre of mass of the
object.
How can you produce angular motion?
A force is applied off centre for angular motion to occur/eccentric force (not through centre of gravity) applied outside centre of mass
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Exam questions 2008
Movement can be described as linear, angular or general motion
(i) Use a practical example to describe how linear motion can be produced
2 marks
(May 2008)
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Exam answers 2008
(i) Use a practical example to describe how linear motion can be produced
2 marks
1. A force is applied through the centre of mass/gravity of the object.
2. A golfer/footballer must hit the ball through its centre of mass/gravity to ensure it travels in a straight line.
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Exam question 2008
1c Explain, using a practical example, how either size or direction of force an affect performance in PE and sport
2 marks
(Jan 2008)
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Exam answer 2008
Explanation [1 mark] 1. Size of force affects how far/fast an object travels
2. Direction of force affects the direction/trajectory of the object/distance a flighted object will travel/if direction of force outside centre of gravity spin will occur/if direction of force is applied through centre of gravity it will cause linear motion
3. Larger size of force causes object to accelerate faster/smaller size of force causes object to accelerate slower
4. Larger size of force causes object to decelerate faster/smaller size of force causes object to decelerate slower
5. Size of force can change an objects shape more/less
Example [1 mark] A snooker player must apply the correct size of force to the cue ball to ensure the
colour ball reaches the pocket.
A golfer must ensure the ball is struck in the correct direction from the tee to hit the green/avoid hazards.
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Exam question 2007
1b (iv) Apply Newton’s 3 Laws of Motion to a strength training exercise
3 marks
(May 2007)
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Exam answer 2007
1b (iv) Apply Newton’s 3 Laws of Motion to a strength training exercise
3 marks3 marks maximum (no application no marks)1 (Law of Inertia/Newtons’ 1st Law)
Weight/performer will not move unless force applied 2 (Law of Acceleration/ Newtons’ 2nd Law)
More force applied greater weight lifted/weight lifted more quickly/athlete must apply force at end of lift to control weight/more weight lifted requires more force to be applied
3 (Law of Reaction/ Newtons’ 3rd Law) Performer pushes against resistance/weight and force applied back against performer
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Exam question 2005
1b When hitting a ball in tennis an understanding of force is important.
Explain how force can cause the ball to:(i) Move straight(ii) Spin
2 marks
(May 2005)
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Exam answer 2005
1b When hitting a ball in tennis an understanding of force is important.
Explain how force can cause the ball to:
(i) Move straight A force is applied through the centre of gravity/mass / the player must hit the ball through the middle (centre of gravity) of the ball.
(ii) Spin 2. A force is applied off centre/eccentric force/hitting a ball on the side will create spin.
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Exam question 2004
1 c During an analysis of practical activities, movement can be described as linear, angular or general motion
Use a practical example to describe how angular motion could be produced
2 marks
(May 2004)
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Exam answer 2004
Use a practical example to describe how angular motion could be produced
2 marks
1. A force is applied off centre for angular motion to occur eccentric force applied outside centre of mass
2. Applied to a sporting example, e.g. player hits/kicks ball at side to create spin/curve
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Learning Objectives
To know and understand Newton’s three laws of motion The types of movement that can be produced
Be able to Apply the laws of motion to explain the type of
movement produced Describe the effect of force in sporting actions
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Home study
Finish preparation for group presentation Any photocopying needs to be given to me by Thursday
lunchtime at the latest Bring any powerpoint presentations on a data stick or email
them to yourself or me
No review test next week
Complete exam questions
Reading in preparation for next lesson Centre of mass - Pages 52-55
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TaskAs a group you must investigate and research the positive and negative
impact of exercise on your disorder and deliver a 10 minute presentation/lesson to the rest of the group
You must include:
• A clear and detailed description of
the disorder
• How it is caused
• Those at most at risk• Consider the positive and negative effects of different types of exercise, e.g.
o Low impact enduranceo High impacto Repetitive actionso Contact activities
• A handout of key information for the rest of the class
• A quick learning task at the end to test how well the group have understood
• Be prepared to be asked questions at the end
• Presentation could be poster or powerpoint based
• Try to include pictures/videos
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Where is the centre of mass?
In a symmetrical/uniform object
COM at geometrical centre
Even distribution of mass around the centre
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COM in humans
• Not uniform symmetrical shapes/composition
o Different heights, mass and compositions of fat, muscle, bone and tissue
• Centre of mass is not at a fixed point
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Changes in centre of mass
• Location is also dependent on body position
• Could be a point inside or outside the body
• With movement centre of mass rarely stays in the same place
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Where is the centre of mass?
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The Fosbury Flop
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Stability
Factors that affect stability and balance in physical activityPosition of athlete’s centre of massPosition of the athlete’s line of gravitySize of the athletes area of support (Number of point in contact with the floor) (Mass of the object)
UNSTABLE LESS STABLE STABLE
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Stability
How difficult it is to disturb a body from a balanced position
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Stability
Position of the athletes centre of mass
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Stability
Size of the athletes support area
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Stability
Position of an athletes line of gravity
Line of gravity
• A line extending from the centre of mass vertically down to the ground
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Exam question (May 2008)
Movement can be described as linear, angular or general motion
(i) Use a practical example to describe how linear motion can be produced
2 marks
• A force is applied through the centre of mass/gravity of the object.
• A golfer/footballer must hit the ball through its centre of mass/gravity to ensure it travels in a straight line.
Q1 & Q2
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Exam question (May 2004)
1 c During an analysis of practical activities, movement can be described as linear, angular or general motion
Use a practical example to describe how angular motion could be produced
2 marks
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Exam answer 2004
Use a practical example to describe how angular motion could be produced
2 marks
1. A force is applied off centre for angular motion to occur eccentric force applied outside centre of mass
2. Applied to a sporting example, e.g. player hits/kicks ball at side to create spin/curve
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Exam Question (May 2006)
Describe how the position of the centre of mass can affect a balance. [3 marks]
1. Centre of mass must be over base of support to hold a balance
2. If Centre of mass moves close to the edge of the base of support balance becomes less stable
3. If Centre of mass/line of gravity passes outside base of support balance is lost
4. The lower the centre of mass the more stable the balance
5. If more points of balance are held balance is more stable
6. Large area of support makes balance more stable
Q6a