Transcript BIOMECHANICS

BIOMECHANICS
Achievement Standard 2.2
Biomechanics
Definition – the study of the body in
motion and, in particular, the forces
that act on a body and the effects
those forces produce.
Biomechanics is the study of cause
and effect. It examines the internal
and external forces on the body and
the effects they produce.
The force is the basis for all
movement.
Newton’s Laws of Motion
Law 1: A body continues in its state
of rest or uniform motion unless an
unbalanced force acts upon it.
An object at rest tends to remain at
rest unless acted upon by some
external force.
For a body to get moving the force
has to be greater than inertia acting
upon it (inertia = bodies tendency to
remain at rest. Greater the mass of
the body = greater the inertia).
Sherriff pg83.
Newton’s 1st Law
illustrated.
Newton’s Laws
Law 2: The
acceleration of an
object is directly
proportional to the
force causing it, is in
the same direction as
the force, and is
inversely proportional
to the mass of the
object.
When a force acts
upon a mass, the
result is acceleration
of that mass.
Newton’s Laws
Law 3: Whenever
a force is applied
there is an equal
and opposite
reaction.
When a force acts
upon a mass, the
result is
acceleration of that
mass.
FORCE SUMMATION
To give an object momentum in
activities such as throwing, kicking,
or striking an object, the amount of
momentum given to the object is
determined by ‘the sum of all forces
generated by each body part’.
To gain maximum momentum, the
force needs to be generated by:
– Using as many segments of the body as
possible.
Force Summation Cont.
– In the correct sequence, using large muscles
first and then the smallest muscles last but
fastest.
– With the correct timing.
– Through the greatest range of motion.
PROJECTILE MOTION
As soon as a body becomes airborne
it is a projectile.
3 factors influence a projectiles flight
path:
– SPEED: the speed at which the
projectile is released
– ANGLE: the angle at which the projectile
was released (optimum angle 45
degrees)
– HEIGHT: height of release can influence
horizontal distance covered.
Projectile Jet Planes
Make a paper jet plane.
When throwing jet plane, manipulate
projectile variables to achieve
maximum distance.
E.g. throw from different heights –
standing, on your knees, on a chair.
Use fast and slow hand speeds.
Try different angles of release.
Questions
Write a paragraph/sentences
explaining how the application of
force summation can influence the
distance you throw a tennis ball.
Explain using Newton’s 1st Law, why
a person weighing 60kg would lose a
sumo wrestling fight against a 100kg
person (mention inertia).
Questions
Rank the following in order of their mass from
lowest to highest:
– Softball
Ping-pong ball
– Basketball
Shot
– Hockey ball
Which of the above balls would have the greatest
amount of inertia?
If you were applying force to overcome inertia
it would be:
–
–
–
–
Greater for the softball or the basketball?
Less for the ping-pong ball or the shot?
Greater for the hockey ball or shot?
Less for the softball or hockey ball?
LEVERS
A lever is used when you want to apply
more force. Most levers have three
clearly identified parts:
1. The fulcrum – the pivot point around
which the movement happens. In body
levers this is usually the joint.
2. The load – the weight that needs to be
moved (resistance).
3. The force – the place where force is
applied. In the body this is the effort
produced by the muscles contracting.
Levers
Can you think of any household
tools/machinery that act as levers?
Function of a Lever
2 main functions:
To increase the resistance that can be moved
with a given effort e.g. crow bar.
To increase the velocity at which an object
will move with a given force.
There are three classes of lever:
– First class
– Second class
– Third class
The human body consists mainly of third class
levers. Third class levers generate speed rather
than force. We can increase the velocity at which
an object can move with a given effort. V = M / S
Levers in Sport
In some sports the equipment you use
acts as an extension of the levers in your
body and helps to generate greater force
or speed.
Give some examples of levers in sport.
Longer levers result in more speed,
beneficial for striking and throwing
objects.
Shorter levers result in greater strength,
beneficial for pushing, pulling, and lifting
objects.
Questions
Johnny needs some help with his
tennis serve. He has a low success
rate with not many serves making it
over the net.
You need to come up with 3 coaching
pointers using Biomechanical
Principles and Functional Anatomy
that will help improve the success of
Johnny’s serve.
CENTRE OF GRAVITY
The point at which all parts of an object
are equally balanced.
Standing up right our centre of gravity
is around our navel.
The centre of gravity changes
depending upon what position the body
is in.
The centre of gravity can lie outside an
object.
Generally, the lower the COG the more
stable an object will be.
LINE OF GRAVITY
The vertical line that passes through
the centre of gravity to the ground.
The line of gravity is important when
determining the stability of an
object.
If the line of gravity falls within an
object’s base of support the object is
relatively stable (and vice versa).
BASE OF SUPPORT
The area within an object’s point of
contact with the ground.
The larger the area the base of
support covers, the more stable an
object will be.
QUESTIONS
Copy each of the
objects and draw
in the centre of
gravity.
Which player is
more stable?
Explain using the
words base of
support, line of
gravity and COG.
MOTION
Linear motion – is in a straight (vertical)
line. All parts of the body move in the
same direction and at the same speed.
[Give examples]
Angular motion – occurs around an axis.
This can be internal (body parts rotating
around a joint) or external e.g. ………..
General motion – a combination of linear
and angular. This is the most common of
all movements, as most human movement
requires rotation of body parts around
joints e.g. ……….