1	Chapter 5 Stability
2	Stability Related to: Mass Inertia Momentum Stability is a battle of Torques
3	Equilibrium, Balance, and Stability Equilibrium implies coordination and control When an athlete is in control he/she can neutralize those outside forces that would disrupt performance
4	"The female gymnast counteracts the..." The female gymnast counteracts the forces that would tend to pull her off of the beam
5	"The sprinter leans far forward..." The sprinter leans far forward and would fall on his face, except he counteracts the pull of gravity by pushing backwards and downwards The force is not directed through the CG therefore it produces a Torque opposite to that of gravity
6	Static and Dynamic Equilibrium Athletes must maintain balance in skills where there is virtually no movement, and in skills where there is much movement and change of direction.
7	Stability This refers to how much resistance the athlete puts up against having their equilibrium disturbed The more stable the athlete the more resistance the athlete puts up against disruptive forces.
8	Linear Stability Directly related to mass, inertia, and momentum Increase in any of these and stability increases An athlete who is more massive is harder to move An athlete who is moving in one direction is harder to move in another direction The greater the momentum an athlete has the harder it is to stop him.
9	"Some athletes want to move..." Some athletes want to move in a straight line, like an 8 oared crew. Some do not want to go in a straight line, but want to change directions often, like slalom downhill skiing. Sometimes too much body mass is too much stability.
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11	Linear Stability and Friction Wrestler lying on a mat is hard to move because of gravity and the friction between the mat and the body. The friction in speed skating is minimal, and the athlete can be easily knocked over if her base of support shifts too rapidly. But some friction is necessary in order to change directions and not slip and fall over.
12	Rotary Stability Is the resistance of an athlete or an object to being tipped over, or spun around in a circle. The destabilizing force can be gravity, air resistance, an opponent, or other external forces. The destabilizing force produces a Torque, and this could around almost any axis in their bodies.
13	Increasing Stability 5 Ways: 1) Mass: The greater the mass of the object the more stable it is to an external force. A 450 pound sumo wrester is more stable than a 200 lb wrester of the same height. Which one is easier to knock over?
14	"2)" 2) Base of support: The larger the base of support the greater the stability Stand with your feet together and have someone push you from the side. Then spread your legs 3 feet apart and be pushed again. Which one is more stable?
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16	"3)" 3) Height of the CG above the base of support: The lower the CG to the base of support the more stable. Stand with your feet one foot apart and have someone push you from the side. Then lower your CG closer to the base of support and be pushed again. Which one is more stable?
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18	"4)" 4) The line of gravity should be nearest to the side that is receiving the external force. Stand with your feet two feet apart, and put your weight over your left foot, and have someone push your right side. Then shift your weight to your right foot and be pushed again. Which one is more stable?
19	"5)" 5) If the base of support is extended toward the oncoming force there is more stability to resist the force. Receiving a blow from a blocker In pitching a throw done from a wide base of support allows the ball to be accelerated over a much longer distance, increasing V.
20	When the CG is below the base of support as in suspension sports there is automatic stability
21	Neutral Stability is Shown in a Ball where the CG is always over the Base of Support as long as the surface is level If the surface is on an angle the line of gravity is not over the base of support and the ball will roll.
22	Stability is related to Torque
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24	"When walking and running one..." When walking and running one has to get their CG outside the B of S in order to destablize the body and fall forward. Stability is regained as the B of S is extended.
25	Acceleration and Dynamic Stability If the CG is outside of the B of S then the body will fall, unless the Ground Reaction Forces produce an Acceleration to counter the gravitational forces pulling the body down.
26	Rotary Stability When Twisting, Turning, or Spinning The more angular momentum, the more stability: I ω The more moment of inertia, or the more angular velocity or both. We can add to Newton’s first law of motion: an object that is rotating will rotate at a constant angular velocity and in a plane, unless acted upon by an unbalanced torque.
27	What about the plane of motion during rotation? This is also called the gyroscopic effect. The plane of motion of the object around the axis of rotation resists having the plane of motion or the axis of rotation tilted. Objects that show the gyroscopic effect: Football, spinning balls, discus, bicycle wheels