Physical EducationUnit 1

AREA of study 2

Biomechanical movement principles

Pages 62 - 135

Labs Classwork Homework Participation/Attendance (80%)

Work Requirements

Case study analysis or data analysis◦ Week 4 - 5 (term 2)

Assessment Tasks

Biomechanics is the study of living things from a mechanical perspective and is essentially the physics behind human movement.

The application of the laws and principles of mechanics to living organisms.(Mechanics of Sport 1997)

The science of human movement. It applies the laws of mechanics and physics to human performance. (Live It Up 2006)

What is biomechanics?

A scientist who is involved in:◦ Human performance analysis◦ The analysis of forces in sport and physical

activities◦ How injuries occur in sport◦ Injury prevention and rehabilitative treatment

methods◦ The design and development of sporting

equipment.

What is a biomechanist?

Cinematography Computer and digital analysis Wind tunnels Resistance pools/swimming flumes Electromyography

What technology/equipment does a biomechanist use?

Motion Force production Application of force Newton’s three laws of motion Momentum Leverage Impact and friction Balance and stability **Equipment design**

Topics we will cover:

KEY KNOWLEDGE KEY SKILLS Newton’s laws of motions incorporating

force, mass and weight, acceleration and inertia applied to a range of sporting and physical activities.

The application of force summation to different sports and physical activities

How is momentum conserved and transferred during different sports

Factors affecting angular motion including torque, angular velocity, momentum and moment of inertia and their application to sporting activities

The coefficient of restitution and elasticity of different sports equipment.

How does rebound velocity effect performances?

Explain the application of key biomechanical principles to a range of sporting movements by using correct terms

Investigate and interpret graphs of biomechanical principles pertaining to movements

Participate in, analyse and report on a range of practical activities that consider biomechanical principles

Use biomechanical principles to critique the effectiveness of different movements

Analyse different sporting actions to identify similarities and differences as well as the correct application of biomechanical principles to improve performance

The body’s resistance to change its state of motion.◦ Resistance to beginning movement ◦ Resistance to changing its movement whilst

moving. The heavier an object, the greater its

inertia. Eg.

Inertia

They’re different!

• Mass is the amount of matter an object is made up of. Mass is usually measured in kilograms.

• Weight is the force exerted on an object by gravity and is directly proportional to its mass.

Mass & Weight

“A push or a pull acting on an object.”◦ (from this year’s text)

“Any pushing or pulling activity that tends to alter the state of motion of a body.”

Forces on the body can be internal or external.

Examples of forces...

Forces

Gravity◦ The pull towards the centre of the earth.

Friction◦ The rubbing of the surface of one thing

against that of another. Air resistance

◦ The resistance against a body created by air. Water resistance

◦ The resistance against a body created by water.

External Forces

Friction is the force that occurs whenever one body moves across another surface.

Friction always opposes motion.

Friction

Occurs when two objects slide over one another.

Eg.

Sliding Friction

Rolling Friction When an object rolls across a surface. Eg.

There are two types of internal forces: Isometric force (without motion)

◦ Muscular contractions create force without changing length or creating movement.

◦ Eg. Isotonic force (with motion)

◦ Force is sufficient enough to change the state of motion.

◦ Eg.◦ Eg.

Internal Forces

Sub-maximal force◦ Using a less than maximal force to create a

successful, more accurate performance.◦ Eg.

Maximal force (force summation)◦ Can be achieved:1. Simultaneously, where an explosive action of

all body parts occurs at the same time.◦ Eg.2. Sequentially, where body parts move in

sequence.◦ Eg.

Internal Forces

Lab #5 due

Friday, 3rd May

Pages 101-102

Newton’s first law of motion◦ inertia

Newton’s second law of motion◦ Acceleration/momentum

Newton’s third law of motion◦ Action/reaction

Newton’s Laws of Motion

‘A body will remain at rest or continue in a constant state of motion unless acted upon by an external force.”

Examples...

Newton’s First Law of Motion: Inertia

‘A force applied to an object will produce a change in motion (acceleration) in the direction of the applied force that is directly proportional to the size of the force.’

Examples...

Newton’s Second Law of Motion: Acceleration/Momentum

‘For every action there is an equal and opposite reaction.’

The total momentum of two objects before impact or contact will equal the total momentum after impact.

Newton’s Third Law of Motion:

Action/Reaction

“The motion possessed by a moving body.”

Momentum = mass X velocity The greater an object’s momentum, the

further it will travel and harder it is to stop. Which has greater momentum:

◦ A marathon runner weighs 60kg and is jogging at 10kmh.

◦ A footballer weighs 90kg and is walking at 6kmh.(Momentum is measured in kg m/s)

Momentum

•An object that is not moving has zero momentum because it has no velocity

•If two objects have the same mass but different velocities, the one moving quickest has the greater momentum

•If two objects have the same velocity but different masses, the one with the greatest mass also has the greater momentum

Total momentum before a collision equals total momentum after the collision (but can be affected by external forces)e.g.

•A hockey stick is used to hit a stationary ball (zero momentum before being hit)•Before hitting the ball the stick has all of the momentum which is then transferred to the ball at point of impact (the stick still has momentum during the follow through)

Conservation of Momentum

Page 106 Questions 1, 2, 3, 4 & 5

Thinking things through

The momentum of a rotating object or body. AM = moment of inertia X angular velocity

Angular Momentum

Is a body’s resistance to beginning rotation. The greater the distance from the axis to the

end of the body (ie. to head of tennis racquet), the greater the moment of inertia.

Moment of Inertia = mass x radius2

Eg.

Moment Of Inertia

Angular momentum is conserved when a body is in flight and there is an inverse relationship between angular velocity and moment of inertia

Conservation of Angular Momentum

What can coaches/parents do to reduce the moment of inertia of children’s sporting equipment?

Moment of Inertia

Impulse = force X time◦ Where force equals velocity or speed, and time is

the length of time over which the force was applied.

Impulse is the reason objects’ momentums change.

To change an object’s momentum, a force must be applied to the object over a period of time.

Impulse

The amount of rebound potential of a ball. When a ball hits a surface it changes shape

for a short time before rebounding and returning to its previous shape.

Factors affecting CoR:◦ Contacting surfaces◦ Temperature◦ Impact velocity

Coefficient of RestitutionImpact

CoR is calculated by using the following formula:◦ CoR = height of rebound

height of release

Object Height of release

Height of rebound

CoR

Golf ball 2m 1.6m 0.894

Tennis Ball 1m 0.6m 0.775

Coefficient of Restitution

Ball Height of release Height of rebound Coefficient of restitution

Tennis ball 1m

Hockey ball 1m

Nerf ball 1m

Basketball 1m

Table tennis ball 1m

Soft-cross ball 1m

CoR - carpet

Ball Height of release Height of rebound Coefficient of restitution

Tennis ball 1m

Golf ball 1m

Soccer ball 1m

Basketball 1m

Squash ball 1m

Soft-cross ball 1m

Nerf ball 1m

Table tennis ball 1m

Soft ball 1m

CoR - concrete

Page 117

Chapter Review Questions