Why do footballs curve when they are kicked?

Chances are you watch football and see top professionals like Cristiano Ronaldo put an insane amount of swerve, or curve, on their shots or passes. But why do footballs curve when they are shot or passed? There are two very easy explanations for why footballs curve.

According to research, the smoothness of a ball improves its curve. The Adidas Jabulani ball used at the 2010 World Cup was criticised at the time for its liveliness and unpredictability. That ball featured less stitching with long straight pieces of leather. Balls with more stitching, such as the Brazuca which was used at the 2014 World Cup in Brazil, do not move about as much as smoother balls. 

One of the interesting aspects of balls with smoother surfaces is it can curve the opposite way compared to balls with more stitching. When a player passes or shoots a football he/she applies spin on the ball. That spin is increased due to the stitching and smoothness of the ball’s surface.

Right-footed players pass the ball from right to left, while left-footed players pass the ball from left to right. A smoother ball bends the opposite way. For example, right-footed players will see their passes go left to right with a smooth surfaced ball. Therefore, shots or crosses would bend away from the direction goalkeepers would traditionally expect the ball to go.

Why do footballs curve when they are kicked? How to bend a ball

Bending a ball is an art and top players like Ronaldo have mastered the skill.

• Take an approach at a slight angle and hit the ball with the inside of your striking foot
• Hit the ball with the inside of your foot at the point where the big toe and foot meet
• Your foot should strike under the ball to give it lift

By putting bend on the ball, players can fool defenders with cross and shots.