The 2014 World Cup soccer tournament is an opportunity to understand that soccer is not only one of the most popular sports in the world, but can also be used as an interesting tool to examine many physical phenomena from everyday life. In the article before us we will try to examine some of the basic laws of physics and see how they are reflected in the football game
Soccer is not only one of the most popular sports in the world, but can also be used as an interesting tool to examine many physical phenomena from everyday life. In the article before us we will try to examine some of the basic laws of physics and see how they are reflected in the football game.
More of the topic in Hayadan:
- Watch: NASA turns the 2014 FIFA World Cup into a lesson in aerodynamics
- A smart ball, and sensors on each player - FIFA World Cup 2014 model football
- See a soccer game from the point of view of the ball
- By 2050, robots will be able to beat the world champion in soccer
- The science of FIFA
Newton's first law - The law of persistence
According to Newton's first law, any object will continue to move at the same speed it was moving as long as no force acts on it. This means that a force must be applied to cause the object to change its velocity. For that matter, if a ball is standing on the grass at rest, that is, its speed is constant and equal to zero, when we kick it hard, we exert force on it and thus make it change its speed according to the direction and strength of the kick. After the kick, the ball continues to move at a decreasing speed due to a counter force exerted on it by the air and then the grass - That is the force of friction, and this force continues until its speed finally drops to zero. If we were playing soccer in space, the ball would move at a constant speed after the kick, and since the friction was minimal it would continue at the same speed for an enormous, and theoretically infinite, distance.
Newton's second law - The law of force, mass and acceleration
According to Newton's second law, the acceleration of an object is directly proportional to the sum of the forces acting on it. From Newton's first law we learned that when we kick the ball it changes its speed. This change is called acceleration and it depends on the strength of the force applied to it and its direction. When we kick the ball with force, its speed increases in a short time from zero to a high speed, therefore it is said that its acceleration is high. After the kick, the force we applied no longer acts on it and the ball stops accelerating. At the same time, the frictional force of the air, followed by the friction of the grass, acts on it and this force acts against the direction of movement, causing it to spin and gradually reducing its speed to zero.
On the occasion of the 2014 Soccer World Cup, the author of this article, Dr. Erez Gerti, was interviewed on the program of Tal Berman and Aviad Kissos starting at minute 31:35.
So we have two main forces that act on the ball - the kicking force, which causes the ball to accelerate to a high speed, and the frictional force, which causes it to slow down to zero speed. Now we will add another parameter to the equation - the mass. Mass is an expression of the amount of matter, and on Earth it can be treated like weight. The greater the mass, the more power we will need to increase the acceleration, which of course makes sense. Since most footballs have more or less the same mass, it can be ignored in our example, but if we look at the force exerted on a soccer ball compared to the force exerted on a heavy iron ball, we find that it takes much more force to propel the iron ball the same speed and distance.
Newton's Third Law - The law of action and reaction
According to Newton's third law, every action has a reaction equal in magnitude and opposite in direction. This means that when a player kicks a penalty kick into the goal and the goalkeeper jumps and blocks it, the goalkeeper causes the speed of the ball to decrease at once from a high speed to zero, i.e. exerts a damping force on it. The ball, on the other hand, exerts on the player a force equal in strength and opposite in direction. Since the player's mass is much higher than the ball's, the force exerted by the ball on him has almost no effect on the player's movement. However, goalkeepers can testify that they feel a tangible force hitting their hands when they stop a goal kick, sometimes even pushing them back.
To watch the video on Newton's three laws of motion.
momentum
Momentum is a measure of an object's direction of motion and its strength, and is defined by multiplying its mass by its velocity. When a player passes a ball to his friend, he transfers his momentum to the ball, that is, his leg moves, hits the ball, and as a result, the ball moves in the direction and force he received from the leg. When the ball reaches the other player, the player gently slows it in motion, effectively reducing its momentum to zero. The player then kicks again and gives it momentum again, and with a little luck and a lot of skill might even hit the net. Another factor that reduces the momentum of the ball is the friction with the grass and the air.
Ballistic movement
When we pick up the ball with a kick, it moves in an arc and finally lands on the grass. This thing happens because we do kick it at some angle in the air, but an additional force acts on the ball - Force Earth's gravity. When we kick the ball we give it power in two directions: up and forward. The ball moves away from us, and therefore does not receive any more force from us, but two forces continue to act on it: the force of friction that slows its forward movement and the force of gravity that acts on it from top to bottom. As a result, the ball loses height and its movement takes on an arcuate shape. We also see the same phenomenon in firing shells from a cannon or shooting a basket in basketball.
You are welcome to watch the video that explains about Ballistic movement
Magnus effect
In a soccer tournament that took place in 1997, the Brazilian player Roberto Carlos kicked an amazing free kick from a distance of 30 meters, sidestepped the defensive wall of the players and scored an amazing goal that seemed to defy the laws of physics. There is no doubt that this is a kick that requires a lot of practice and skill, but the physics behind it is very simple.
When you kick the ball not in its center but at its edge, we make it spin around itself, it creates a kind of air vortex around it, so that even if the player no longer directly affects its movement, the ball can still change its direction in the air. When the speed of the ball's movement decreases due to friction with the air, the vortex created around it due to its rotation affects its trajectory and causes it to change its direction in an arcuate motion. To an onlooker it seems as if the ball has a will of its own. This phenomenon is called the "Magnus effect".
This is how the Magnus effect works The diagram is taken from Wikipedia; Created by me
Carlos' famous kick in slow motion. Pay attention to the movement of the ball and its rotation in the middle of the road
There are many more physical principles that can be learned from the game of soccer - For example, how does the position of the center of gravity affect stability (perhaps this is the reason why there are quite a few short soccer players); the ripple effect that goes through the crowd at big games; And even the ideal amount of air in the ball for optimal performance. So the next time you watch football, try to identify more interesting physical phenomena, especially in the great virtuoso stars, and feel free to correct anyone who says "it contradicts the laws of physics".
Food for thought - BBack to you
How would a change in the environmental conditions affect the phenomena we talked about, for example a heavier ball, a smooth court or playing in conditions of zero gravity?
Gerty Cedar
Davidson Institute for Science Education
Weitzman Institution of Science
One response
Smoother pitch play occurs when there is heavy rain. The friction of the surface with the ball decreases, which causes a lower swing and makes it harder for the players, who have to run faster, while the friction of the sole of their shoe with the grass decreases, which can cause slipping....