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 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

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 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 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

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