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# The Physics Of Soccer

## on Dec 20, 2009

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## The Physics Of SoccerPresentation Transcript

• The Physics of Soccer By Ben Miller
• Roberto Carlos’ Impossible Kick
• From 30 meters out, Roberto Carlos (from Brazil) kicked a ball with the outside of his left foot and curved the ball around a wall of defenders into the right upper ninety of the goal.
• A ball boy standing ten meters away from the goal ducked because he thought he was going to get hit.
• THE IMPOSSIBLE SHOT
• PROOF ?
• The Brazilian fans loved this shot, but many spectators thought he had cheated somehow.
• Physics, as well as the hundreds of players who do it every day, prove this shot can be made.
• PHYSICS BEHIND THE SHOT
• Carlos said he knew he could make the shot because he had practiced during every meeting the team had, but he did not know the forces of physics involved.
• WHAT’S INVOLVED?
• There are four forces that have to take place in order for this shot to work:
• Force of the kick (velocity)
• Drag
• Gravity
• Magnus force
• FORCE BEHIND THE KICK
• This is the force that makes the ball move in the first place.
• Causes the ball to move in a linear trajectory at a certain speed if no other forces are involved
• DRAG
• Drag is caused by air viscosity.
• If a ball is kicked, then it will eventually stop because drag is moving in the opposite direction.
• GRAVITY
• Gravity is a force that acts on all objects.
• It pulls objects downward toward earth at an acceleration of 9.8 m/s².
• If a ball is kicked, then it will eventually stop because gravity is pulling it down at a constant rate against earth’s surface.
• BERNOULLI’S PRINCIPAL
• BERNOULLI’S PRINCIPAL
• Magnus force is similar to Bernoulli’s principal: “When a fluid flows, it has kinetic energy because of its motion. It also has gravitational potential energy, or stored energy, due to the Earth's gravitational field. If the fluid picks up speed, or accelerates, it has more kinetic energy than before.”
• GUSTAV MAGNUS
• MAGNUS FORCE
• Magnus force is caused when there is pressure on both sides of an object moving through the air or a fluid.
• If there is a decrease in pressure on one side of the object, then the object will start to curve in that direction.
• EXAMPLE: AIRPLANE WING
• While flying, the air on top of the A plane’s wings are wing has to travel further than the designed for lift. air on the bottom of the wing because there is a curve on the top of the wing. This causes a decrease in pressure on the top of the wing because the air is moving faster on the top than on the bottom c causing lift.
•
• MAGNUS FORCE ON BALL
• If a soccer ball is kicked with top spin, then the ball will fall to the ground faster because gravity is helping pull it down.
• If a soccer ball is kicked with down spin, the opposite happens, but gravity will eventually pull it down.
• WHAT DID CARLOS DO?
• Roberto Carlos kicked the ball with oblique spin, causing the ball to arc with the decrease in pressure and also causing gravity to pull the ball down right before it missed the net.
• This made the “impossible” shot possible with a perfect curve around a wall of defenders and into the net.
• ANOTHER CURVED SHOT
• RESULT
• This new kind of finesse inspired soccer players all over the world to start curving soccer balls into the net.
• A famous player, David Beckham, uses this skill in almost every game he plays.
• It also brought nations and communities together to watch this improved sport, while showing scientists what the human body can do.
• BEND IT LIKE BECKHAM
• RESULT CONT.
• Brought on many studies of how balls act in different conditions due to their shapes, weights, etc.
• Started research to keep players in every sport from cheating by scuffing balls or weighting them to fly through the air differently.