Page 9 - class-XI-ch.8-Lesson notes

gravity is over its base of support and the line of gravity falls within the base. The greater the body surface in contact
with the ground, the larger is the base of support.

Types of Equilibrium
There are two types of equilibrium, i.e., static equilibrium and dynamic equilibrium.

1. Static Equilibrium: Static equilibrium is when the centre of gravity is in a stable position, e.g., when one is sitting or
performing a handstand in gymnastics.

2. Dynamic Equilibrium: Dynamic equilibrium is a state in which the centre of gravity is in motion, e.g., when one is
running or performing a cartwheel in gymnastics.

Principles of Stability
In sports and games, stability is usually referred to as a balance. The body's ability to maintain stability or balance is
governed by the following principles.
1. The lower the centre of gravity is to the base of support, the greater is the stability. When performing any activity
that requires stability, an individual should lower his centre of gravity.
2. The nearer the centre of gravity is to the centre of the base of support, the more stable is the body. When the
centre of gravity extends beyond the boundaries of the base of support, balance is lost. Keeping the body/s
weight centre over the base of support.
3. Stability can be increased by widening the base of support. Widening the base of support helps in achieving
greater stability.

Centre of Gravity
All individuals and objects have a centre of gravity, which can shift depending on the position or movement of the
individual or object.
"A centre of gravity is an imaginary point (within or outside the body or object) around which the body or
object is balanced.”
It can be said that the centre of gravity is the point at which all of the body/s mass seems to be located and the point
about which an object would balance. The centre of gravity is continuously changing during movements. It can be
either within or outside the body depending on the shape of the body. It always shifts in the direction of movement.
When an individual stands erect with his/her hands at the sides, the centre of gravity is located at the level of the
hips. The knowledge of centre of gravity is important for sportspersons to better their skills. For example, basketball
player during a jump ball swings both arms forward and upward that assist in gaining height. Once in the air, the
player allows one arm to drop to his side and tries to get maximum reach with the other arm.