Ding Ning's tomahawk serve toss height

[Superdragon]

The controversy continues—in her semi-final match against Shibata Saki, Ding Ning had a let called against her for not tossing the ball high enough on one of her tomahawk serves. She obviously isn't comfortable tossing the ball higher with the tomahawk, as she finished the match without attempting it again.

What is wrong with tossing the ball higher on the tomahawk? Can't she just practice and adjust her timing to strike the ball?

 

[ttmonster]

A clean tomahawk is not an easy serve to do , needs a lot of agility and flexibility , Kenta is probably the cleanest you can find .... and talking about bad tosses , Lin Gaoyan was pretty much tossing parallel to the ground into this own body for the reverse pendulum and he got away with it everytime ...

The controversy continues—in her semi-final match against Shibata Saki, Ding Ning had a let called against her for not tossing the ball high enough on one of her tomahawk serves. She obviously isn't comfortable tossing the ball higher with the tomahawk, as she finished the match without attempting it again.

What is wrong with tossing the ball higher on the tomahawk? Can't she just practice and adjust her timing to strike the ball?

 

[NextLevel]

The controversy continues—in her semi-final match against Shibata Saki, Ding Ning had a let called against her for not tossing the ball high enough on one of her tomahawk serves. She obviously isn't comfortable tossing the ball higher with the tomahawk, as she finished the match without attempting it again.

What is wrong with tossing the ball higher on the tomahawk? Can't she just practice and adjust her timing to strike the ball?

If you have developed a serve for many years to a high level without the rules being enforced against you, it can be very hard to fix the serve and feel that it is performing at the same high level because the ball toss change requires timing changes. This is true for *any* serve. In fact, it is easier to pretend you are learning a new serve than to try to fix a high level serve.

In Ding Ning's case there is a crouch that comes forward into the ball that needs to be timed with the ball coming to the height of the table and a higher toss would require her to stay in that crouch much longer or go into that crouch later. These timing issues mean that at the very least, under pressure, she will revert to what she can time properly. And at her level, just about every time she uses that serve means that she is under pressure.

 

[zeio]

From the physics standpoint, the higher the toss, the harder it is to time, theoretically.

The velocity of the ball drop increases 9.8m/s every second. Say, your normal toss reaches you after 1 second of drop, your window of contact would get compressed in 1/2 if the toss goes higher and reaches you after 2 seconds, 1/3 after 3 seconds, so on and so forth.

 

[Superdragon]

I didn't work out the physics, but I get everything else.

I've watched the serve that was called a let many times, and it was clearly not close to a 16cm toss. There is no way that Ding Ning isn't aware of this, but she continues to try and get away with it. She must have figured out that overall she will win many more points on the tomahawk than she will lose on fault calls, so she doesn't bother to practice the serve with a higher toss.

I wonder what would happen if she were called for a fault EVERT TIME she tossed the ball too low. Would she practice a higher toss for the tomahawk, or would she abandon it?

If you have developed a serve for many years to a high level without the rules being enforced against you, it can be very hard to fix the serve and feel that it is performing at the same high level because the ball toss change requires timing changes. This is true for *any* serve. In fact, it is easier to pretend you are learning a new serve than to try to fix a high level serve.

In Ding Ning's case there is a crouch that comes forward into the ball that needs to be timed with the ball coming to the height of the table and a higher toss would require her to stay in that crouch much longer or go into that crouch later. These timing issues mean that at the very least, under pressure, she will revert to what she can time properly. And at her level, just about every time she uses that serve means that she is under pressure.

From the physics standpoint, the higher the toss, the harder it is to time, theoretically.

The velocity of the ball drop increases 9.8m/s every second. Say, your normal toss reaches you after 1 second of drop, your window of contact would get compressed in 1/2 if the toss goes higher and reaches you after 2 seconds, 1/3 after 3 seconds, so on and so forth.

 

[tropical]

Basic Physics course at 10th grade, anyway... assuming the playground is in vacuum. ha ha...

d = V[SUB]o[/SUB] T + gT[SUP]2[/SUP]/2

From such equation, and know that V[SUB]o[/SUB] is always 0 at highest toss, to get a full 1 sec the height must be ~ 5m For 16cm toss it only takes 0.18 sec if my math is correct!

 

[bircham boi]

I wonder what would happen if she were called for a fault EVERT TIME she tossed the ball too low. Would she practice a higher toss for the tomahawk, or would she abandon it?

But this simply takes us back to the same old debates about calling illegal serves. I wonder what would happen if EVERY toss that wasn't vertical was called? I wonder what would happen if EVERY toss that was hidden was called?

 

[Superdragon]

If this were to happen, than perhaps Par Gerell and Anton Källberg would have to choose alternate professions.

In all seriousness, I'm a multiple sports fan for many years and it really bothers me when rules aren't enforced, or selectively enforced. What's the point of having them then?

But this simply takes us back to the same old debates about calling illegal serves. I wonder what would happen if EVERY toss that wasn't vertical was called? I wonder what would happen if EVERY toss that was hidden was called?

View attachment 16614

 

[yoass]

From the physics standpoint, the higher the toss, the harder it is to time, theoretically.

Yes, quite so. Up to terminal velocity, that is.

The velocity of the ball drop increases 9.8m/s every second.

I don't think so. With a mass of about 2.8g and a diameter of 40mm, air friction is far from negligable resulting in a substantially lower acceleration, and a relatively low maximum free-fall velocity.

You're still right of course, but not that pronounced.

 

[Andy44]

Yes, quite so. Up to terminal velocity, that is.


I don't think so. With a mass of about 2.8g and a diameter of 40mm, air friction is far from negligable resulting in a substantially lower acceleration, and a relatively low maximum free-fall velocity.

You're still right of course, but not that pronounced.

Got me interested in finding the actual terminal velocity of a ping pong ball. According to this paper, terminal velocity at sea level is about 8 meters/second. It takes roughly half a second to get there. Most interesting, a toss of a meter and half (~5 feet) is more than you need to get all the falling speed you can get. So those super high toss serves may help to throw off the receiver's rhythm, but they're unnecessary for serve quality.

 

[zeio]

Yes, quite so. Up to terminal velocity, that is.



I don't think so. With a mass of about 2.8g and a diameter of 40mm, air friction is far from negligable resulting in a substantially lower acceleration, and a relatively low maximum free-fall velocity.

You're still right of course, but not that pronounced.

Good point.

I skipped the drag because it'd open a can of worms. Drag is difficult to deal with as it increases non-linearly with velocity, and involves air density, which depends on temperature and humidity even at sea level. It wasn't until 2014 that JTTA commissioned a study that finally measured the values of drag with 40mm celluloid ball for the range of speed typically seen in table tennis matches. From the data, the terminal velocity comes out to roughly 8.96m/s, which is quite far away from the 8m/s from the study Andy44 cited, or the 9.2m/s from another study, as opposed to the calculated 8.89m/s, probably because of the higher temperature and the generic coefficient of drag.

Whatever the case, I'll let Ding Ning explain the reason behind her low toss.

 

[Tinykin]

......... Most interesting, a toss of a meter and half (~5 feet) is more than you need to get all the falling speed you can get. So those super high toss serves may help to throw off the receiver's rhythm, but they're unnecessary for serve quality.

To me, 5ft(1.5m) is a super high toss.....poor me

 

[yoass]

Got me interested in finding the actual terminal velocity of a ping pong ball. According to this paper, terminal velocity at sea level is about 8 meters/second. It takes roughly half a second to get there. Most interesting, a toss of a meter and half (~5 feet) is more than you need to get all the falling speed you can get. So those super high toss serves may help to throw off the receiver's rhythm, but they're unnecessary for serve quality.

Well, sure. But consider this: given that the ball reaches terminal velocity after falling ±1.5m. If you toss between 0 and 1.5m, you'll have to deal with acceleration prediction, with a somewhat complex friction coefficient in the equation.

Once you've reached terminal velocity the ball movement is a linear function. Probably much easier to time ball contact if the last bit of its trajectory is traversed with constant speed, I'd guess. Maybe we should ask He Zhiwen. I think I also recall high tosses by Jacques Sécretin, not sure if he still answers the phone…

 

[tropical]

Velocity is one factor, time is another. Linear or not it is not that important. For sure the higher the toss the more difficult it is to deal with as air current from air conditioning system in the room can also contribute in making it more difficult to players.