Simple Science
How do footballers curve their
free kicks?
At a glance
Footballers kick the
side of the ball causing
it to spin
In the footballing world a select
few possess an incredible
power over the ball. They are
able to curve the flight of the
ball in ways that the rest of us
can only imagine. Just what is
going on in these cases?
© David Ingham 2
Air moving around the
ball moves faster when
it’s moving in the same
direction as the spin
Air moving around the
ball in an opposite
direction to spin moves
slower
This difference in air
speeds causes an area
of lower pressure to be
created on the side of
the ball where the air
is moving faster
The ball feels a force
towards the area of
low pressure and so
begins to curl
The amount that the ball curves during flight is entirely due to the spin
which is put on the ball when the player kicks the ball. Kicking the ball
on its side causes the ball to spin in a direction which is dependent
upon the side of the ball which is kicked. As the ball spins, it causes air
to flow around it faster in the direction it is spinning. The faster the air
is moving the lower the air pressure. This means that the ball feels a
force towards the lower pressure causing the path of the ball to curve.
In many cases the ball does not curve immediately but goes straight
before curving at the last minute. If the ball is moving fast enough
then it creates a turbulent air parcel around the ball allowing the ball
to move in a straight line. As the ball slows down, the air begins
flowing smoothly around the ball causing it to swerve.
Centre for Lifelong Learning
Alex Brown, 2012
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