One of the main reasons serve reception in volleyball is so challenging is because of the movement of the ball. Floater serves change direction unpredictably, and jump serves drop suddenly. Sometimes, the ball moves in ways the server never even intended.
The Evolution of balls
When I started playing, volleyballs were plain white. To improve visibility, colored balls were introduced, and over time, their designs were updated. In 2019, Mikasa changed their ball design again, and the new V200W became the official FIVB match ball.
Why have ball designs changed so often?
While business reasons certainly play a role, we should also acknowledge the developers’ relentless pursuit of creating a “higher quality ball.”
Let’s look at the ball manufacturing concepts of two major companies, starting with Mikasa.
Mikasa’s Ball Manufacturing Concept
The company’s website highlights the concept behind their new V200W ball:
“The V200W features an 18-panel aerodynamic design that optimizes visibility and flight stability. The ball’s surface, a microfiber material with a dimpled and multi-pattern structure, stabilizes the ball’s trajectory while enhancing its cushioning performance. Additionally, a Nano Balloon Silica coating prevents the ball from getting slippery from sweat.”
Now, let’s look at Molten, another major manufacturer of sports balls.
Molten’s Ball Manufacturing Concept
According to an interview with a Molten ball development manager, their philosophy is “For the real game.” Their goal is to create balls that go exactly where the player intends them to go. The manager noted that they want to reduce unpredictable, “wobbly” balls, even in soccer, because they’re impossible for the kicker to control.
From this, it’s clear that both companies are driven by a singular goal: to create a ball that allows players to control it exactly as they intend.
Why the Ball Still Moves Unpredictably
Despite the tireless efforts of developers, balls still sometimes behave in ways players can’t fully control. The most common examples are the “floater serve” in volleyball and the “wobbly ball” in soccer. Players may even intentionally use these unpredictable movements to their advantage.
Because of this, it’s crucial for players to understand the physics behind why a ball moves in unintended ways.
The Physics of Ball Movement
Let’s break down the principles of ball movement, starting with why a non-spinning ball “wobbles.”
How a Floater Serve Wobbles
- The ball is hit. Immediately after contact, the ball’s speed is at its maximum and begins to slow down. The ball has no spin.
- Air resistance. As the ball moves forward, air resistance pushes back.
- Karman vortex street. Without spin, which stabilizes air flow, a trail of alternating vortices forms behind the ball. This is called a Karman vortex street. This phenomenon not only creates drag but also pushes the ball in unpredictable directions.
- The ball wobbles. The Karman vortex street causes the ball to change its trajectory in ways the hitter never intended.
Now, let’s look at the physics behind a topspin ball, which is common in jump serves.
How a Topspin Ball Drops
- The ball is hit. Immediately after contact, the ball’s speed is at its maximum and begins to slow down. The ball has topspin.
- Air pressure differences. On the top of the ball, the ball’s rotation and the airflow move in opposite directions, creating an area of high pressure. On the bottom, the ball’s rotation and the airflow move in the same direction, creating an area of low pressure.
- Magnus effect. Air flows from high pressure to low pressure. Because of this, the ball is pushed downward. This phenomenon is called the Magnus effect, which is why a topspin ball drops.
Understanding Ball Physics Changes the Game
Analyzing volleyball from a physics perspective is incredibly valuable. Many experienced players and coaches tend to rely on their intuition and years of experience, which is an invaluable asset. However, this “implicit knowledge” can be difficult for others to understand and may only be a partial, or even an incorrect, solution.
In contrast, physics is a well-established and highly reliable science. By understanding the principles behind ball movement, players can better analyze and improve their own performance. This knowledge can help them troubleshoot why a ball moved in an unexpected way, leading to smarter adjustments and the development of new, more effective tactics.
