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Heading a ball is a really important skill to learn in order to control
the ball falling down towards to a player. When a person is heading a
ball, the same physics applied to the ball as when it was kicked. The
collision is the last process of heading a ball, this also happens in
kicking the ball, however it is easier to demonstrate when viewing the
physics viewpoint from heading a ball.
The Elastic Collision
- - When
a ball is kicked by a player and it is traveling through the air,
soccer players get a little competition to get it first by heading the
ball. As shown in previous page, when a player kicks the center or
off-center of the ball, the ball comes with certain velocity and
acceleration. The law of conservation of energy is always applied.
There will always be the air drag force that acts on the opposite
direction of the path of the ball. The ball will be spinning and
curving at the same time if the player kicked the off-center of the
ball, because of the Bernoulli's principal and Magnus effect. When a
player heads the ball, and elastic collision happens. What is the
elastic collision? The elastic collision is when the total kinetic
energy of two objects before a collision is equal to the total kinetic
energy of the two objects after the collision. So the total kinetic
energy before the ball hits someone's head is equal to the total
kinetic energy after the collision. When the ball hits a person's head
when the head is at rest, some of the momentum energy in the ball is
transferred to the head. That is why the head has to move back when the
ball hits the head, thus the ball will change direction with a certain
angle when it comes in contact with the head (as you can see in the
equation). That is why the players are heading towards the ball so they
also can transfer the momentum energy to the ball in order to
accelerate or maintain the speed of the ball (Usually the purpose of
heading is to change the direction of the ball with the same velocity.
So sometimes there's a situation when a player doesn't need to
accelerate the speed of the ball by heading but maintain it by heading
towards the ball with acceleration, so the total momentum energy
remains in the ball).
Conservation of momentum
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Summary of Bibliography
http://en.wikipedia.org/wiki/Elastic_collision Wikipedia
The
Science
of
Soccer
by
author
Wesson,
John
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