Name: 网球职业选手在选球时会看什么（What tennis pros look at when they pick a ball）
Uploaded: 2021-08-05T06:35:43.000Z
Duration: 5 min 29 s
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Novak Djokovic will bounce the ball, first with his racket,

and then finally move his hair to the back of his ears.

But there's one ritual almost every player does:

Choosing a tennis ball with the perfect level of fluffiness

And some players believe the right ball can help them win.

But does fluff actually make a difference?

players typically ask the ball boy or girl for 3 or 4 balls,

And most of these players are looking for something specific:

“I try to get the ball that is more new for the first serve.”

Daniil Medvedev is a professional tennis player

who's currently ranked Number 2 in the world.

He just competed in the Ultimate Tennis Showdown.

“You try to find a ball that has less hair, actually,

that has a lot of humidity in it for the first serve,

Michael Kosta, a former professional tennis player,

I felt like that moved faster through the air.

It gave me more confidence to hit that first serve,

and I would save the kind of juicier, bigger, fluffier ball

for my second serve, as almost a safety ball--

I need this big, slow, beach ball to get it in the court,

“On the second serve they're looking for control more than speed.

I'm working with Serena Williams, For the last, almost ten years.”

“When the ball is fast, you have less control.

So on the second serve, they don't want to hit a double fault.

And the fluffier the ball, the more grip you have.”

“It's the kind of tactic that, I should say, doesn't affect so much.

Like, you're not going to win the match just because you chose a fluffier ball.”

But there is some science behind this ritual.

So, Rabi, how involved, or how much information do you know about tennis?

“Oh, I think I know enough to be dangerous.

Dr. Rabindra Mehta works for the NASA Ames Research Center,

and has been studying the aerodynamics of sports balls

With tennis, you get what we call 'extra drag.'

Drag is the force that slows the ball down

Initially, when you pull it out of a can,

you'll find it's pretty compact, and so it has one level of drag on it.

it tends to fluff up, initially, the first few games,

Like the hair on our arms, it'll contribute to the drag.”

That's why swimmers have their own ritual

of shaving all their body hair before big meets:

to make it easier for them to move through the water.

To figure out how much the fluffiness of a ball

Dr. Mehta and his team used a wind tunnel.

“We had the ball on the balance, so we could measure

how much drag force, how does it change?”

They compared tennis balls with different amounts of wear,

and proved that the fuzzier the ball, the slower it moves.

“And the way we proved that was just by literally shaving the ball,

to try and get it to match the other balls.

that if a player serves with a fluffier ball,

the person receiving gets slightly more time to react.

And the server then gets slightly more time to return it.

“I was at the US Open, and we had some people there

who were interested in what we were doing, and they actually sent us balls

that had been used in the actual tournament.

So when we started looking at those balls, it was pretty obvious

that they were preferentially using two or three balls out of the six.

So it wasn't like there was equal wear.”

Beyond the science, the ball selection still serves a purpose:

“If I believe, when I'm match point down, and I have to hit a second serve,

that my rituals, of finding that bigger, juicier, feltier ball,

are going to give me a tiny little bit of safety on the second serve,

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网球职业选手在选球时会看什么（What tennis pros look at when they pick a ball）

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ultimate

ritual

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