Kinesiology Unit 8 1

Definition of Balance: An individual’s ability to control stability 2

To achieve a balanced state, the two forces acting on the object – it’s 1.weight and 2.the vertical reaction provided by the support – must be equal in magnitude and must lie in the same vertical plane 3

Also called CENTRE OF MASS Body’s Balance or Pivot Point Definition of Centre of Gravity: The point about which a body’s weight is equally balanced in all directions In the human body the centre of gravity is not fixed because the body is made up of many segments that can move or stay stationary at any moment in time 4

Two methods have been used to locate the centre of gravity: 1. Segmental/Suspension Method (In Motion) 2. Reaction Board (RB) Method (Motionless) 5

Single segmental objects have their Centre of Gravity directly above the base of support. Sometimes the Centre of Gravity can be found outside the body. (Arc) 6

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Another Example: 8

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Definition of Stability: A resistance to a disruption in the equilibrium of the body 10

If a body in equilibrium is given a small displacement from its equilibrium position, one of three things will happen: It will keep going in the same direction (unstable equilibrium) or It will stop in the position it has been moved (neutral equilibrium) or It will return to its original position (stable equilibrium) 11

A rotating body will continue to turn about its axis of rotation with constant angular momentum unless an external couple or eccentric force is exerted upon it Also known as: The principle of conservation of angular momentum 12

The angular acceleration of a body is proportional to the torque causing it and takes place in the direction in which the torque acts 13

Newton’s second law 14

For every torque that is exerted by one body on another, there is an equal and opposite torque exerted by the second body on the first 15

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