Why does a shuttlecock turn when you hit it?

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📓 The short answer

A shuttlecock turns when you hit it because most of the mass sits near the compact cork, while the wide skirt catches most of the aerodynamic resistance. That offset creates a torque that flips it cork-forward within about 20 milliseconds of impact.

📚 The long answer

The sport of badminton is unique in a lot of ways. It is the fastest racket sport, with the shuttlecock reaching over 200 mph (~322 km/h) upon impact (yes, that's faster than tennis). It also consistently ranks in the top five most popular participatory sports in the world — in 2004, it was second to soccer/football.

But the thing that distinguishes badminton the most is its feather-adorned, conical-shaped shuttlecock, which quickly flips each time you hit it. Let's get into the physics that explains this high-speed, flip-flop behavior.

What is a shuttlecock?

A shuttlecock is the feathered projectile that badminton players hit over the net, aiming to land it in their opponent's court boundaries. Weighing roughly five grams, the shuttlecock is made out of 16 goose feathers (or plastic ones) planted into a cork.

Its name comes from "shuttle," referring to its back-and-forth movement across the net, and "cock," referring to its resemblance to a rooster.

While it can reach incredible speeds immediately after impact with the racket, a shuttlecock's skirt creates a large amount of drag, or aerodynamic resistance, causing it to rapidly slow its speed.

Why does a shuttlecock turn when you hit it?

When a badminton racket hits a shuttlecock, it may initially start flying backwards, tilted, or sideways. But in ~20ms (0.02 seconds), the shuttlecock turns with the cork facing forward.

The shuttlecock's conical shape is what causes it to flip rapidly upon impact. But what about this shape contributes to the flip?

A shuttlecock has two distinct parts: the cork and the skirt. The cork is small and heavy, which means that most of the shuttlecock's weight is near the cork. The skirt is much larger in surface area, so most of the drag occurs on the skirt as the shuttlecock moves.

Two key points shape how a shuttlecock moves: the center of mass and the center of pressure.

The center of mass, the average position of all mass of an object, is located very near its cork since that's where most of the shuttlecock's weight is concentrated. However, the center of pressure, the point where the net aerodynamic force effectively acts on the object, is located closer to the skirt because that is where it catches and deflects the air.

A key thing to note here is that the center of mass and center of pressure are not located in the same location, with the center of mass being about 3.4 cm in front of the center of pressure. This difference is what makes the shuttlecock rotate in flight.

When the shuttlecock is facing skirt-forward, air pushes hard on the skirt. Because the center of pressure (on the skirt) and the center of mass (near the cork) are offset, this creates a twisting force, or torque, that rotates the shuttlecock until the cork is pointing forward.

This flip happens incredibly fast. After a 1 ms contact with the racket, the shuttlecock flips in about 20 ms. Then there's about an 80 ms period where the shuttlecock oscillates before setting into stable flight. Blink and you'll miss it!

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🧠 Bonus brain points

Who invented the sport of badminton?

Badminton is a sport with ancient origins. Hitting shuttlecocks and keeping them in air has been a pastime for people all around the world for at least 2,000 years.

There is evidence of various forms of badminton being playing in China, Japan, Greece, North American indigenous tribes, India, Siam, and more. It's gone by different names, like "battledore and shuttlecock" in Europe or "hanetsuki" in Japan. And it's been played with different materials, like bundles of corn husk with feathers in the Zuni game "Po-ke-an."

The contemporary badminton most people play today was formalized in the 1860s by British army officers during the British occupation of India. Originally called "Poona" in reference to its place of origin in present-day Pune, the players introduced a net to divide a court.

The game later made its way to Badminton House, the country estate of the Duke of Beaufort in Gloucestershire, England, where it was further popularized and eventually took on the name we use today.

--- Thanks for reading this week's newsletter! If you have any thoughts, questions, or favorite GIFs, my inbox is always open. Just hit reply to send me a note! :) ​ All my best, Caitlin ​Click here to read five facts about Caitlin​

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​Sources for this week's newsletter​

🌐 Wikipedia article of the week

​Art competitions at the Summer Olympics​

"Art competitions formed part of the modern Olympic Games during its early years, from 1912 to 1948.... Medals were awarded for works of art inspired by sport, divided into five categories: architecture, literature, music, painting, and sculpture, which led to the events' initial moniker of "Pentathlon of the Muses.
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The juried art competitions halted after a 1949 decision by the IOC that since the majority of art contestants worked as professional artists, the competitions contradicted the Olympic spirit of amateur competition, which was more strictly enforced for athletes."

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