Kicking a soccer
“foot” ball
By Marta Bakowska-Mathews
15/01/2013
PHY 3091 Spring 2014
Introduction
• Aspects of soccer ball movement:
pressure/type of cleats one is
wearing/material of
ball/force/direction/air pressure
• I will use Newton’s laws of
motion/Bernoulli’s principle/Law of
Conservation of Energy
Why?
• Over 1/6th of the population watches or plays soccer
making it the world’s most popular sport
• There are many different kinds of way of kicking a ball
• I play soccer for FSU and plan to go professional after
college
• Many people don’t know that there is a scientifically
correct way of kicking a soccer ball to maximum effect
• Soccer players don’t learn how to kick a ball using
physics. They do it by practice (foot eye coordination)
About the soccer ball
• What is it made of:
Inside (bladder) – latex rubber or butyl
Outside (layers) – polyester or cotton
Used to be made out of leather which absorbs water
• Perfect sphere with dimensions:
Circumference: (68.6-71.1cm/27-28inches)
Weight: (14-16 ounces/0.392-0.448kg)
http://www.walmart.com/cp/Socce
r-Balls/1075746
Formulas/Principles
• Bernoulli’s principle: a relationship
between the pressure of fluid and its
speed around an object
• Newton’s First Law: F = ma
• Kinetic Movement Formula: K = ½ mv^2
• Law of Conservation of Energy:
PE(f) + K(f) = PE(i) + K(i)
PE(i)=PE(f)=0
What initially happens when you
kick a soccer ball
•
•
•
•
•
Kinetic energy from your foot and leg is transferred to the ball
The ball deforms slightly (0.01 seconds)
Heat is released and the ball moves (↑deform=↑heat loss)
v(ball)>V(leg)
e is coefficient of restitution (0-1) = speed of ball bouncing up
compared to ball hitting ground
http://www.seriousgoalkeeping.net
/Documents/PhysicsofKickingSoccer
Ball.pdf
Basics of kicking
a ball straight
Ways of kicking a soccer ball
• Inner spin (inside of foot)
• Outer spin (outside of foot)
• No spin pass (side of foot)
• Power (laces)
http://www.footballboots.co.uk/12361-phelon-bootreview.html
Continued
• The lower you kick the ball the higher it will
go
• Counter clockwise spin – right/move left
• Clockwise spin – left/move right
• Middle – power/straight
http://paybymobilephone.com/nike-soccer-ball-flickrphoto-sharing.html
Kicking a ball with side spin
• Kick it off center (left or right)
• Air moves over ball faster on one side (left) causing less pressure on
the other (right)
• Ball moves from high to low pressure (Magnus)
•
•
•
The ball goes straight first
The slower the ball goes the more it
curves
Dimples cause air resistance (golf)
http://www.footy4kids.co.uk/soccerphysics.htm#
Beckham Free kick
http://www.youtube.com/watch?v=XiPZuA9-HDY
Kicking the ball with backspin
• Hit ball slightly below center
• Air moves faster above ball creating
lower pressure there
• Ball moves from high to low pressure
making the ball hang in the air longer
Kicking the ball with top spin
• NOT POSSIBLE
• The ball cannot go through the ground
• It will hurt you foot, bounce a little, and
not go anywhere
Who kicks harder, a short or taller
person?
• It is commonly thought that the bigger and
taller you are the harder you can kick it
• Mass of small person leg = 7 kg
• Mass of tall person leg = 11 kg
• Same leg velocity = 25 m/s
• Average mass of a ball is 0.42 kg
• e = 0.7
www.seriousgoalkeeping.net/Documents/PhysicsofKicki
ngSoccerBall.pdf
Continued
• Short person:
v(ball) =
7
25
(1+0.7)
7+0.42
= 40.1 m/s
• Tall person:
v(ball) =
11
25
(1+0.7)
11+0.42
= 40.9 m/s
www.seriousgoalkeeping.net/Documents/PhysicsofKicki
ngSoccerBall.pdf
Continued
• 40.1 m/s vs. 40.9 m/s
• Almost the same velocity
• Smaller person’s leg should be faster since it takes less
energy to move a smaller mass
• The difference comes in the velocity of the leg
• If smaller person can have V(leg) = 30 m/s, v(ball)
becomes 48m/s!!!!
www.seriousgoalkeeping.net/Documents/PhysicsofKicki
ngSoccerBall.pdf
Conclusion
• There are many different ways to hit a ball:
with your foot/on the ball
• Don’t try and get topspin because you will
just hurt yourself!
• Many aspects to getting the ball from a to b
• Enhance your soccer skills with these
principles
• But remember, kicking is just one part of
soccer
References
http://www.footy4kids.co.uk/soccer-physics.htm#
http://www.unc.edu/~ncrani/kicking1.htm
http://www.seriousgoalkeeping.net/Documents/PhysicsofKicking
SoccerBall.pdf
https://thescienceclassroom.wikispaces.com/Physics+of+Soccer
Questions?