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| IT'S ALL ABOUT VECTORS |
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Sometimes, you have to use your head when
you do a header. If you try to aim the ball into the net it
may go wide. Why? Because it's all about vectors. Since the
"angle of incidence equals the angle of reflection", try
heading the ball towards where it was served. The combinations
of vectors (the motion of your head , the motion of the ball,
and the bounce -reflection- off your noggin) will direct the
ball into the net... GOAL!! | |
| HOW A PHYSICIST'S BRAIN WORKS |
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When a soccer ball is kicked, it is
compressed. Assuming the ball is struck through its center,
the amount of compression depends mostly on the pressure in
the ball, initial velocity of the ball and the speed of the
foot striking the ball with the mass of the leg and the mass
of the ball being two additional variables but, these last two
do not vary much.
What does a physicist ask
him/herself?
- How much compression takes place for a reasonable set of
parameters?
- How long in time is the ball incontact with the foot?
- How far do the foot and ball travel while they are in
contact?
- What makes the ball spin? Is it striking the ball off
center, or is it a movement of the foot away from a path
through the ball's center during the period of contact, or
both?
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| HOW HIGH WAS THAT GOAL KICK?
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Suppose a goal kick is booted 36 feet into
the air. When it finally comes down, it bounces up off the
grass 12 feet. The formula for the coefficient of restitution
(c) is , where h=the bounce height and
H=the drop height.
The coefficient of restitution is a measure
of the elasticity of the collision between the ball and the
ground. Elasticity is a measure of how much bounce there is,
or in other words, how much of the kinetic energy of the
colliding objects before the collision remains as kinetic
energy of the objects after the collision.
A perfectly elastic collision has a
coefficient of restitution of 1. Example: two diamonds
bouncing off each other. A perfectly plastic, or inelastic,
collision has c=0. Example: two lumps of clay that don't
bounce at all, but stick together. So the coefficient of
restitution will always be between zero and one.
In the above example, c=0.58. If the ball
had bounced up only 6 feet, the coefficient of restitution
would have been 0.41
How do you think the height of the grass,
moisture, and temperature might affect the coefficient of
restitution? | |
| HE DID THE MATH FOR YOU! |
 Leonhard Euler was one of top mathematicians
of the eighteenth century and the greatest mathematician to
come out of Switzerland. He made numerous contributions to
almost every mathematics field and was the most prolific
mathematics writer of all time. It was said that "Euler
calculated without apparent effort, as men breathe...." He was
dubbed "Analysis Incarnate" by his peers for his incredible
ability.
Euler's polyhedral formula states that, for
any simply connected polyhedron, the number of faces (F) minus
the number of edges (E) plus the number of vertices (V) is
always equal to 2, or stated mathematically: F - E + V 2
For a soccer ball, which has the shape of a
truncated icosahedron with 32 faces, 90 edges, and 60
vertices: 32 - 90 + 60 2 | |
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