PRINCIPLES OF STABILITY
THE RELATIONSHIP OF THE BODY TO SPACE
NEWTON'S THREE LAWS
LAW OF INERTIA
Objects must be acted upon by outside source
How much force would it take to move a mass?
Answer -
That point where all weight is centered around.
The CG of a symmetrical object of homogeneous density, is the
exact center of the object
When mass in is not constant, CG shifts in the direction of greater
mass.
Locating the Center of Gravity
As projectile,
Locating the Human BodyCenter of Gravity
Stability and Balance
Stability:
Factors that affect:
Foot position affects standing balance
Track Start
Stability here is a state of equilibrium (State of Rest
of a Body).
STABILITY IS ALSO THE DEGREE (OR MEASURE) OF EQUILIBRIUM.
FOUR PRINCIPLES OF EQUILIBRIUM
3 - RELATE TO ________________________________________
1 - RELATES TO
STABILITY IS DIRECTLY PROPORTIONAL TO THE AREA OF THE BASE.
IE:
STABILITY IS DIRECTLY PROPORTIONAL TO THE DISTANCE OF A POINT
FROM THE FORWARD EDGE OF THE BASE.
IE:
STABILITY IS INVERSLY PROPORTIONAL TO THE HEIGHT OF THE CENTER
OF MASS.
MEASUREMENT OF STABILITY-WHILE AT REST
PATHAGRIUM THEORUM, COMBINED WITH THE FORMULA FOR DETERMINING
STABILITY
FORMULA FOR STABILITY
STABILITY = Ht.cog X Wt.
Ht.cog = Height that the center of mass has to be raised to make
one unstable.
An object with c o g 4 ft. high, 3 ft. from edge of base.
Hypotenuse = 5'
Unstable if raised 1'
Wt. = The weight of a person or object (expressed in lbs.)
HOW MUCH STABILITY DOES THE FOLLOWING TRACK ATHLETE HAVE?
C of G = 24 in. from the leading edge
C of G = 30 in. in height
Weight = 195 lbs.
Answer = _________________________________________________
This is the amount of force that would be required to offset this
person's equilibrium
HOW MUCH STABILITY DOES THIS TRACK ATHLETE HAVE?
C of G = 8 in. from the leading edge.
C of G = 30 in. in height
Weight
Answer = _________________________________________________
Is there a difference in the measurement of equilibrium between
the two athletes?
LAWS OF MOTION AS APPLIED TO THE VERTICLE JUMP
WHAT IS THE FIRST THING WE SEE A BASKETBALL PLAYER DO BEFORE
THE TIP OFF
_________________________________________
WHY?
_________________________________________________________________
WHAT IS THE NEXT PRINCIPLE THAT MAY APPLY?
WHEN YOUR FEET PUSH OFF OF THE FLOOR FROM A STANDING POSITION,
WOULD THE FORCE BE AS GREAT AGAINST THE FLOOR AS THE FORCE EXERTED
UPWARD?
Answer? ____________ Why? ______________
Answer?_______________________________
THE STAMP PRIOR TO THE JUMP
WHAT IS THIS FOR? IS IT NECESSARY? WHY?
THE TAKE-OFF
WHAT DOES ONE DO WITH THE ARMS AT TAKE-OFF?
Answer?_______________________________________________
WHY? ________________________________________________
AGAIN - NEWTON'S THIRD LAW - ACTION / REACTION.
WHERE DOES NEWTON'S 2ND. LAW COME INTO PLAY IN THE VERTICLE
JUMP? (LAW OF ACCELERATION)
WHO WOULD YOU PREFER TO BE YOUR JUMP BALL TIPPER? (GIVEN TWO
PLAYERS WITH SIMILIAR LEG STRENGTH AND ABILITY.
A - 6'7" - 280 LB. PLAYER
B - 6'7" - 230 LB. PLAYER
Answer:___________ - WHY? ACCELERATION IS DIRECTLY PROPORTIONAL
TO THE FORCE AND INVERSELY PROPORTIONAL TO THE MASS
WHAT IS ACCELERATION?
RATE OF CHANGE IN VELOCITY.
QUESTION: WHEN IS THE ACCELERATION IN THE JUMP THE HIGHEST?
Answer:____________________________________________________
WHAT IS VELOCITY
THE RATE OF CHANGE IN POSITION OR (DISTANCE)
IE: MPH OR FT./SEC.
WHAT IS DISTANCE IN THE CASE OF THE VERTICLE JUMP
DISTANCE = ____________________
MEASURED IN IN./SEC.
AS YOU REACH THE TOP OF THE TIP, WHAT DOES THE ARMS DO?
__________________________________. WHY?
Answer: __________________________________________________________
REMEMBER, C of G DOES NOT INDICATE BODY POSITION.
IE: HIGH JUMPER - FLOP
IN THE VERTICLE JUMP, AS THE DISTANCE BETWEEN THE HAND AND THE
C of G INCREASES, THE HIGHER YOUR HAND WILL BE.