1. Stability and Newton
PSE4U
Mr. MacMillan

2. 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.

3. Stability is also Affected By:
Collisions
The Surface
Friction
Angle
Inner Ear
Sight
Readiness

4. 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?

5. Increasing Stability Lower the C of G Increase the mass
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

6. 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?

7. 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?

8. Who is this guy Newton

9. Who is Newton 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

10. 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?

11. 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

12. 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?

13. Law of Acceleration (Newton’s Second Law)
Implications for sport movement
Club/racket/bat weight
Follow through
Athlete body weight

14. 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

15. Newton’s Third Law (Action/Reaction)
For every action there is an equal and opposite reaction
What is an example of this?

16. 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

17. Summary Law #1. Objects are Lazy Law #2. F=ma
Law #3. Equal and Opposite
Inertia
Acceleration
Reaction

18. 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

19. Factors Influencing Balance
Location of the center of gravity in relation to the base of support
Size of the base of support
Mass of the person
Height of the center of gravity
Traction/friction
Sensory perceptions

20. So how do balance and Newton’s laws fit together?