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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

Structure of a synovial joint

Features that improve STABILITY

Features that improve MOBILITY

Ligament

Meniscus

Joint capsule

Articular cartilage

Synovial fluid

Bursa

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

Anatomy and Physiology 5

Motion and movement 1

Biomechanics:

Newton’s Laws of Motion

SPORTS BIOMECHANICS

Biomechanics is the study of body movements and of the forces acting on the musculoskeletal system

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

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

Types of motion

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.

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)

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

General motion

A combination of linear and general motion

Identify the types of motion

5

3

4

2

1

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

Force

A push or a pull that alters the state of motion of a body

What can a force do to an object?

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

Effects of force

What factors affect the extent of these effects?

Size of the force (how many Newtons)Application of forceDirection of the force

Motion and movement

Sir Isaac Newton

Video – Newton’s 3 laws of motion

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”

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’

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

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

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

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

Law’s of motion

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

Laws of Motion

http://www.youtube.com/watch?v=UVdqxYyFRKY

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

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)

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.

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)

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.

Exam question 2007

1b (iv) Apply Newton’s 3 Laws of Motion to a strength training exercise

3 marks

(May 2007)

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

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)

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.

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)

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

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

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

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

Where is the centre of mass?

In a symmetrical/uniform object

COM at geometrical centre

Even distribution of mass around the centre

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

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

Where is the centre of mass?

The Fosbury Flop

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

Stability

How difficult it is to disturb a body from a balanced position

Stability

Position of the athletes centre of mass

Stability

Size of the athletes support area

Stability

Position of an athletes line of gravity

Line of gravity

• A line extending from the centre of mass vertically down to the ground

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

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

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

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