Throwing is
only allowed to a goal keeper anytime, but it is also awarded to a
player of a team when the ball was touched by an opposing team player
before it leaves the sidelines, which is also known as throw-in.
Throwing a ball is another good example of how physics work in soccer.
First off, there are different physics between throwing the ball by a
goal keeper and the throw-in. Before we talk about the physics, we need
to know about some soccer rules. Throwing done by a goal keeper is a
free throwing. He can throw a ball with any motion moving within the
goal keeper line. But the throw-in is quite different. A player isn't
allowed to move around, and both feet need to be in contact with the
ground when the ball has been thrown. Also, the player must use both
hands to throw. So it's physically, it is different from a free
throwing ball.
1. Throwing by a goal keeper.
In soccer games, the goal keepers prefer throwing a ball rather
than kicking a ball. It's because of the better accuracy when the ball
is thrown. The reason for this can be explained with the center of
mass.
When a player pass the ball by kicking, there are two way to
pass: no spin on the ball and spinning the ball with a curve. For the
best accuracy, when a player passes the ball with no spin on the ball,
he must kick the exact center of the ball. When a player passes the
ball by spinning it with kick, the player must kick off-center on the
ball in order to spin. Having the right spot to kick, and the reason
behind it were explained in the previous "kicking" page. But in
reality, the most difficult thing in soccer is kicking the perfect spot
where the player wants to kick. (This is also the reason why players
miss shots or passes.)
Throwing a ball is different. When goal keeper is throwing a
ball, the center of the ball is already held on goal keeper's hand (or
at least very near the center of the ball.) Because the surface of goal
keeper's hand has the center of the ball, the ball can stay on his
hands. Under this condition, the goal keeper can throw the ball more
accurately than just kicking the ball.
Another physics theory is involved in this performance. If we
see soccer games, the goal keeper throws a ball with one arm even
though they can throw it with two arms. The reason for this is to
achieve longer acceleration time. Using one arm to throw gives a goal
keeper longer contact with the ball than using two arms (you can try
it). So by throwing a ball with one hand, he gets more time to
accelerate while the ball is on his hand, which will make the ball go
faster and further. It can be also seen in boxing and basketball. In
boxing, swings and hooks are the most powerful moves. It is because
those motions get a longer time to accelerate than just jabbing. In
basketball, three point shooters stretch their one arm as much as they
can to make a score. It's also because the ball gets a longer time to
be accelerated in their control.
2. Throw-in
Let's talk about throw-in now. As already mentioned, in
thrown-in, a player must use both of his hands to throw a ball, and
must keep his both feet on the gound when the ball leaves his hands.
So unlike the goal keeper's throwing, in throw-in, the player can't use
one arm to accelerate the ball longer or can't even throw too hard
because it can make the feet move away from the ground. So most players
don't try to throw it too far in throw-in position. They usually throw
it to whoever is close to them, because it's not easy to throw a ball
in that position. BUT some people made it possible to throw the ball
far in that position, for past years. Watch the following clip.
This is called
flip throw-in or handspring throw-in. As you can see in the clip, this
skill actually worked. He didn't break the rule because he used two
hands to throw the ball and his feet were still on the ground when he
threw it. The reason the ball can be thrown that far is because he
could accelerate the ball by rotating his body so the ball can be in
contact with his body longer. It is a very good idea but it's rarely
used in competitive soccer games. The reason for this is bad accuracy,
which is demonstrated in the next clip.
As you
can see, its accuracy is really bad because you can't see anything when
you are flipping your body.
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Summary of Bibliography
The Science of Soccer by author
Wesson,
John
Youtube.com
