Stability and Motion in Sports: Principles and Applications

Principle of Stability and Its Uses in Sports

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Ans. i. Broad base of support: for greater stability increase the area of the base and lower the centre of gravity as much as is consistent with the activity involved. Examples:
a. a basketball player stops, spreads his feet wide as shoulder line and lowers his CG to dodge the opponent.
b. Defence position of the player in volleyball.   c. Wide stance of a golfer.     d. tackling position of a player in football.
ii. Stability is directly proportional to the weight of the body: the object or a person with heavy weight will have greater stability as compared to person with less weight.
Example: it is difficult to move a heavier person as compared to less heavier person.
On the basis of this principle, wrestling, boxing, judo, etc. are organized according to different age groups.
iii. Direction of an acting force: to start quickly in one direction, keep the CG as high as possible and as near as possible to the edge of the base nearest to the direction of intended motion.
Example: the crouched position in starting a race, the CG is kept high by not bending the knees extremely and by keeping the hips high, also the lean of the body is towards the hands so that the weight rest on the hands. From this position, the movement hands are raised from the ground; motion starts by reason of the pull gravity. This pull is added to the force exerted against the starting block by the feet and thus aids in a quick start.
iv. When the body is free in the air, if the head and feet move down, the hip move up and vice versa.
Example: a. This principle is applied in the high jump in western or velley roll technique at the take of, the head and one foot is thrust up as high as possible. As the head and one leg clear the bar, they are dropped which raises the hips to clear the bar. As the hips are lowered, the opposite leg is raised to clear the bar.
b. This is also used in pole vault, hurdles and jacknife, dive in swimming.

2. State the three law of motion with suitable examples of its application in sports.
Ans. FIRST LAW OF MOTION OR LAW OF INERTIA
According to first law of motion an object at rest will remain at rest or an object in motion will remain at motion at constant velocity unless acted upon by a force.
It also gives the idea that to change the state of rest or uniform motion of a body in a straight line some external agency is needed. This agency is called force.
Example: (a.) A moving football slows down and then stops often sometime. It comes to rest due to the friction between the ground and the ball.
(b.) To take start in sprint races, to lift the opponent in wrestling, to start hammer throw.
SECOND LAW OF MOTION (The Law of Acceleration)
According to Newton’s second law of motion, the rate of change of momentum of a body is directly proportional to the impressed force and takes place in the direction of force.
Example: (a.) A cricket player while catching a ball moves his hands backwards. Initially the ball is moving with a certain velocity. The player has to apply a retarding force to bring the ballot rest in his hands.            (b.) In baseball player hits the ball hard to throw it far away.
THIRD LAW OF MOTION
According to the Newton’s third law of motion, to every action there is always an equal and opposite reaction.
Example: (a.) The swimmer pushes the water in the backward direction with a certain force. Water pushes the man forwards with an equal and opposite force.
(b.) Walking: when a person walks on the road, he presses the ground in backward direction and the ground exerts an equal and opposite force on the person in the forward direction.
(c.) Shooting: when a bullet is fired from a rifle with a certain force (action) there is an equal and opposite force exerted on the rifle in the backward direction (reaction)