Transcript Chapter6x - KTHSYear11PE

Biomechanical
movement principles
Pages 62 - 135




Labs
Classwork
Homework
Participation/Attendance (80%)

Case study analysis or data analysis
◦ Week 4 - 5 (term 2)


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)

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.





Cinematography
Computer and digital analysis
Wind tunnels
Resistance pools/swimming flumes
Electromyography









Motion
Force production
Application of force
Newton’s three laws of motion
Momentum
Leverage
Impact and friction
Balance and stability
**Equipment design**
KEY KNOWLEDGE






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?
KEY SKILLS





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.
Mass & Weight
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.

“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...

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.


Friction is the force that occurs whenever
one body moves across another surface.
Friction always opposes motion.




Occurs when two objects slide over one
another.
Eg.
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.

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.
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


‘A body will remain at rest or continue in a
constant state of motion unless acted upon
by an external force.”
Examples...


‘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...


‘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.




“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)
•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
Conservation of 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)
Page 106
Questions 1, 2, 3, 4 & 5








The momentum of a rotating object or body.
AM = moment of inertia X angular velocity
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.
Conservation of Angular Momentum
Angular momentum is conserved when a body is in flight and there is an
inverse relationship between angular velocity and moment of inertia

What can coaches/parents do to reduce the
moment of inertia of children’s sporting
equipment?

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.



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 Restitution

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
Ball
Height of release
Tennis ball
1m
Hockey ball
1m
Nerf ball
1m
Basketball
1m
Table tennis ball
1m
Soft-cross ball
1m
Height of rebound
Coefficient of
restitution
Ball
Height of release
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
Height of rebound
Coefficient of
restitution

Page 117