Transcript Stability and Newton`s Laws

Stability and Newton
PSE4U
Mr. MacMillan
Principle 1 – Stability
• The lower the centre of mass, the larger the
base of support, the closer the centre of mass
to the base of support, and the greater the
mass, the more stability increases.
Stability is also Affected By:
• Collisions
• The Surface
– Friction
– Angle
• Inner Ear
• Sight
• Readiness
Drawing Diagrams
• Place a large dot where you believe the C of G
is
• Draw a straight line down to show where
gravity is acting on the C of G
• Draw the width of the base of support
• Is the C of G within the base of support?
Increasing Stability
1. Lower the C of G
2. Increase the mass
3. Increase the size of the base of support
- The further the center of gravity (use the line
dropped from it) is from the edge of the base
of support, the more stable the athlete is
Applications of Stability
• What are points in sports you play that you
use maximum force?
• What are points in your day to day life that
you use maximum force?
• Are there times when it is ok to be unstable?
Welcome Junior to Class
• Does he defy the laws of stability?
– If so how?
• Where is his C of G?
• Where is his Line of Gravity?
• What anatomically would help him in these
moves?
• How does he manipulate his body to help him
with these moves?
Who is this guy Newton
Who is Newton
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He had a sweet wig
He ate apples
He named three laws that govern all motion
Led to one of the most important books of
mathematics
• Helped other scientists discover movement on
Earth and of objects in Space
Newton’s First Law (Inertia)
• An object will remain in a constant state unless
otherwise acted on
• This means objects are like teenagers – they are
lazy. They want to keep doing what they are
already doing.
• This means an object will move at the same rate
or continue to not moved unless something else
“makes” it
What is an example of this?
Law of Inertia
(Newton’s First Law)
• Mass is the measure of inertia
– Greater mass = greater inertia
• Implications for sport movement
– Decreased mass USUALLY means
you are easier to move (less
inertia)
– Agonist/antagonist reciprocal
inhibition
Newton’s Second Law (Acceleration)
• F=ma
• Force is proportional to acceleration
• An object will continue at a constant speed in a
linear direction unless acted upon by an outside
force (ex gravity, friction etc)
• The greater the applied force, the greater the
resulting acceleration – provided mass is constant
What is an example of this?
Law of Acceleration
(Newton’s Second Law)
• Implications for sport movement
– Club/racket/bat weight
– Follow through
– Athlete body weight
Law of Acceleration
(Newton’s Second Law)
• Impulse
– Ft = m(vf-vi)
– Without time, it is impossible to generate force
and change velocity
• Momentum
– Ft = (mvf-mvi)
– If masses are different, deficiencies can be
compensated for by increasing speed
Newton’s Third Law (Action/Reaction)
• For every action there is an equal and
opposite reaction
• What is an example of this?
Law of Reaction
(Newton’s Third Law)
• “For every action there
is an equal and
opposite reaction”
• Ground reaction force
• Implications for sport
movement
– Artificial turf
Summary
• Law #1. Objects are Lazy
• Law #2. F=ma
• Law #3. Equal and Opposite
• Inertia
• Acceleration
• Reaction
Equilibrium, Balance, & Stability
• Equilibrium is the state of
zero acceleration (static or
dynamic)
• Balance is the ability to
control equilibrium
• Stability is a resistance to the
disturbance of equilibrium
Factors Influencing Balance
1. Location of the center of gravity in relation
to the base of support
2. Size of the base of support
3. Mass of the person
4. Height of the center of gravity
5. Traction/friction
6. Sensory perceptions
So how do balance and Newton’s
laws fit together?