# What does topspin actually do to the bounce?

#### Gary Duane

##### G.O.A.T.
Before you conclude that this is a "Captain Obvious" question, check your perception.

Think about a ball that is hit 70 mph or more, backhand or forehand, then picture that ball hit with a lot of spin. Then picture that ball spinning with 5000 rpms. 5000 is incredibly high, much faster than most shots, but let's use that as a kind of limit.

What does that ball do as it bounces? Does it pick up more spin, lose spin, or stay about the same?

All my life I've had a perception that high topspin grabs the court and increases the forward pace of the ball. Same thing in table tennis. My impression was that topspin makes the ball take off, leap forward. It takes away from your time. It's like the ball gets to you too soon. In tennis it's like the ball is suddenly past you. You're swinging late.

But is this true?

If this video is correct, a couple things stick out. First of all, on the HC shown the ball is actually move at 33 mph after the bounce and 27 mph on clay. That's a lot slower than I had pictured. Obviously the ball loses speed from the time it is hit, but it loses more speed than I had realized after the bounce.

Even so, is the ball ever really spinning faster than it is moving horizontally?

What do you think? I believe I have an answer, and the answer is not what I expected.

#### jm1980

##### G.O.A.T.
Before you conclude that this is a "Captain Obvious" question, check your perception.

Think about a ball that is hit 70 mph or more, backhand or forehand, then picture that ball hit with a lot of spin. Then picture that ball spinning with 5000 rpms. 5000 is incredibly high, much faster than most shots, but let's use that as a kind of limit.

What does that ball do as it bounces? Does it pick up more spin, lose spin, or stay about the same?

All my life I've had a perception that high topspin grabs the court and increases the forward pace of the ball. Same thing in table tennis. My impression was that topspin makes the ball take off, leap forward. It takes away from your time. It's like the ball gets to you too soon. In tennis it's like the ball is suddenly past you. You're swinging late.

But is this true?

If this video is correct, a couple things stick out. First of all, on the HC shown the ball is actually move at 33 mph after the bounce and 27 mph on clay. That's a lot slower than I had pictured. Obviously the ball loses speed from the time it is hit, but it loses more speed than I had realized after the bounce.

Even so, is the ball ever really spinning faster than it is moving horizontally?

What do you think? I believe I have an answer, and the answer is not what I expected.
When the ball hits the ground, it will lose most of its speed, regardless of the spin on it. But the more topspin it has, the less speed it's going to lose

Last edited:

#### OhYes

##### Legend
I am thinking is there difference between usage of spin in table tennis and real tennis. Somehow seems table tennis players are using it more, like you need to be Nadal while in real tennis you don't.

#### Gary Duane

##### G.O.A.T.
The ball can't magically pick up speed without an external force acting on it.

When the ball hits the ground, it will lose most of its speed, regardless of the spin on it. But the more topspin it has, the less speed it's going to lose
Of course you are right, and this is common sense. The ball is going to lose speed from the friction of air, and we already know that the bounce can't be more than about 1/2 of what the height was at its highest. We know that from a 100 inch height drop reducing to a max of 58 inches. So it's going to lose a minimum of 40% of the height.

Then it's going to lose speed as it bounces.

That's not what my question was initially.

My question was: How fast is a 5000 rmp ball spinning? Or 3000? Or 2000? Obviously if the ball is spinning faster than 33 mph on a HC, it will for sure push the ball forward, a bit like a car's wheels spinning faster than the speed of the car while it is in the air. The same kind of thing that causes a squeal when you floor the gas and the wheels start to turn faster than the car is moving.

#### jm1980

##### G.O.A.T.
My question was: How fast is a 5000 rmp ball spinning? Or 3000? Or 2000? Obviously if the ball is spinning faster than 33 mph on a HC, it will for sure push the ball forward, a bit like a car's wheels spinning faster than the speed of the car while it is in the air. The same kind of thing that causes a squeal when you floor the gas and the wheels start to turn faster than the car is moving.
When the car wheels slip it's because there is not enough traction on the tires to handle all the torque being generated by the engine. I don't see how this applies here

#### Cashman

##### Professional
Obviously if the ball is spinning faster than 33 mph on a HC, it will for sure push the ball forward, a bit like a car's wheels spinning faster than the speed of the car while it is in the air. The same kind of thing that causes a squeal when you floor the gas and the wheels start to turn faster than the car is moving.
This is an imperfect understanding of the physics involved. The ball is not a perfect sphere where its torque and spin interacts with the court surface in isolation. A lot of what we understand to be the behaviour of different kinds of spin when bouncing is actually linked more to the impact trajectory that we are creating by applying the spin through the air, or how the ball deforms and reforms before and after impact.

http://www.tennisindustrymag.com/articles/2004/04/follow_the_bouncing_ball.html

Last edited:

#### Wurm

##### Rookie
My impression was that topspin makes the ball take off, leap forward. It takes away from your time.
When you're playing the ball's trajectory just prior to and after the bounce plays tricks on you. The brain does see, particularly head on, a heavily spun topspin ball apparently slowing right down prior to the bounce as the spin leads to a transfer of momentum from the forward direction to a downwards one... and then post bounce the ball apparently shoots forward again.

Last edited:

#### Gary Duane

##### G.O.A.T.
This is an imperfect understanding of the physics involved. The ball is not a perfect sphere where its torque and spin interacts with the court surface in isolation. A lot of what we understand to be the behaviour of different kinds of spin when bouncing is actually linked more to the impact trajectory that we are creating by applying the spin through the air, or how the ball deforms and reforms before and after impact.

http://www.tennisindustrymag.com/articles/2004/04/follow_the_bouncing_ball.html

Note that they talk about what happens with topspin and slice, and they talk about the difference in angle of bounce from different spins. However, the one thing they do not mention is the answer to my question: how fast does the ball spin in relationship to the speed forward.

I have that answer now, and it's interesting, at least to me.

#### jm1980

##### G.O.A.T.
This is actually a more interesting question than I thought it was. Rethinking it, there are a couple of possible ways for the horizontal speed to actually increase after the bounce:

1. If the ball hits the surface at a steeper angle than after the bounce, then we could have some of the vertical speed being "converted" into horizontal speed.
2. The spin on ball when it hits the ground can cause friction to push it forward. For example, if you apply topspin to a ball and drop it directly down (horizontal speed is 0), it will still bounce forward

However, my intuition still tells me these effects are negligible compared to the effects of friction and other energy losses on impact to make your regular groundstroke actually end up moving faster than when it came in

#### Gary Duane

##### G.O.A.T.
When the car wheels slip it's because there is not enough traction on the tires to handle all the torque being generated by the engine. I don't see how this applies here
I was computing in mph, and I got 39.1955 by using the average diameter, so that matches my results. The difference between speed of rotation for different diameter balls is so small that it really does not matter here.
It doesn't except in terms of visualizing what happens when the spin is faster or slower than the forward speed.

I got my answer from @Cashman. I used his link. One of many things I did not know is that when spin is as fast backwards as the forward movement (speed) then the two factors will cancel each other out. So if, for example, a ball is sliced with 3000 rpms and is moving at the moment of the bounce at 23.5 mph, immediately afterwards the ball will not be spinning. I did not know that. I had guessed it though.

What this means is that we can mentally get a rough idea of the spin of the ball at the time it is hit on a groundstroke.

But what I was getting at, and what surprised me, and what is not in the link, is that at no time does a ball ever spin as fast as it moves in a forward direction. This means that there is always some degree of skid.

#### Gary Duane

##### G.O.A.T.
This is actually a more interesting question than I thought it was. Rethinking it, there are a couple of possible ways for the horizontal speed to actually increase after the bounce:

1. If the ball hits the surface at a steeper angle than after the bounce, then we could have some of the vertical speed being "converted" into horizontal speed.
2. The spin on ball when it hits the ground can cause friction to push it forward. For example, if you apply topspin to a ball and drop it directly down (horizontal speed is 0), it will still bounce forward

However, my intuition still tells me these effects are negligible compared to the effects of friction and other energy losses on impact to make your regular groundstroke actually end up moving faster than when it came in
But that's what I found out. What you have in mind can't happen unless you can somehow hit a ball with enormous topspin that is moving pretty slow. It could happen for sure in a lob, and we've all see that. A guy put as much spin as possible on a lob to make the ball come down faster, and when the ball hits it takes off because of the extra spin.

However, for normal groundshots the spin is always slower than the speed of the ball.

#### TheIntrovert

##### Hall of Fame
Im not sure I understand the question. Are you asking why the ball slows down so much?

#### TheIntrovert

##### Hall of Fame
It doesn't except in terms of visualizing what happens when the spin is faster or slower than the forward speed.

I got my answer from @Cashman. I used his link. One of many things I did not know is that when spin is as fast backwards as the forward movement (speed) then the two factors will cancel each other out. So if, for example, a ball is sliced with 3000 rpms and is moving at the moment of the bounce at 23.5 mph, immediately afterwards the ball will not be spinning. I did not know that. I had guessed it though.

What this means is that we can mentally get a rough idea of the spin of the ball at the time it is hit on a groundstroke.

But what I was getting at, and what surprised me, and what is not in the link, is that at no time does a ball ever spin as fast as it moves in a forward direction. This means that there is always some degree of skid.
There is. That’s why the Hawkeye always shows an elongated mark of the ball

#### Gary Duane

##### G.O.A.T.
There is. That’s why the Hawkeye always shows an elongated mark of the ball
That makes perfect sense. But until you mentioned that, it never occurred to me.

There are two things that I had wrong. Because of slow motion footage I assumed that the ball was actually picking up a bit of speed immediately after the bounce, from spin. I knew that didn't happen on flat strokes or slice. But I thought with guys like Rafa hitting up to 5000 rpms the ball would actually spin faster than it was moving. I suppose if I had thought about it more I would have realized that was wrong.

So when I did the math and found out that a 5000 rpm shot is spinning almost exactly at 40 mph, suddenly I realized how wrong I was. But I thought there was more skid than there is after figuring that out because I did not realize how much forward speed any ball loses between being hit and immediately after the bounce.

It turns out that for some shots it's pretty close to even. But the shot has to be a bit on the slow side for an ATP player, and with a max of spin.

Even Rafa does not normally hit with 5000 rpms. The norm is more around 3000, and quite often lower than that. 3000 rpms is around 23 mph. and 2000 is around 16 mph.

I'm very interested in facts that totally negate our intuition when reality is clearly different from what we think.

#### ChrisRF

##### Hall of Fame
I think because we are under the impression of Nadal’s "moonballing" we think that generally topspin lets the ball bounce higher. But that’s untrue I believe. A ball with the same loop before the ball bounces but without topspin jumps higher, but not as much forward of course.

The problem with Nadal’s topspin balls is not the pure height at one point, but that it stays high for a longer way forward. So it’s too high to control for many meters, and the opponent has no real comfort zone anymore. Only if Nadal hits a bad shot into the service field it is possible to play it normally on the baseline AFTER letting it fall down.

In table tennis it is more visible that topspin is a shot which makes the ball jumping flatter in reality.

#### Tshooter

##### Legend
Topspin beats Roger, no?

#### Gary Duane

##### G.O.A.T.
I think because we are under the impression of Nadal’s "moonballing" we think that generally topspin lets the ball bounce higher. But that’s untrue I believe. A ball with the same loop before the ball bounces but without topspin jumps higher, but not as much forward of course.

The problem with Nadal’s topspin balls is not the pure height at one point, but that it stays high for a longer way forward. So it’s too high to control for many meters, and the opponent has no real comfort zone anymore. Only if Nadal hits a bad shot into the service field it is possible to play it normally on the baseline AFTER letting it fall down.

In table tennis it is more visible that topspin is a shot which makes the ball jumping flatter in reality.
The link that @Cashman used explains some things that seem counter intuitive, but you have to read the whole thing.

Apparently topspin causes the lowest bounce, backspin the highest, with a flat ball in between. But that is not what we experience because the height of a topspin shot is so high, and a slice is so low.

In other words, if I am understanding correctly, if you have a topspin shot crossing way over the net, and a slice hit hard that barely gets above net high, what you will see is a high bounce for the topspin. I'll see if I can find the exact place where that is mentioned...

#### Wurm

##### Rookie
Apparently topspin causes the lowest bounce, backspin the highest, with a flat ball in between. But that is not what we experience because the height of a topspin shot is so high, and a slice is so low.
Yes, but only if the trajectory of the ball is the same.

Imparting those spins leads to different trajectories leaving the racquet for a start, but also a heavily spun topspin shot can be travelling close to vertically prior to the bounce as the affect of spin and friction with the air (the Magnus Effect) pushes the ball downwards.

#### Gary Duane

##### G.O.A.T.
Here it is:

"Topspin bounces lower than backspin in the lab. What are the consequences of this? It means that for two balls hitting the court at the same angle and speed, but one with topspin and the other with backspin, the topspin ball will come upon you faster and lower than a backspin ball. Lower, because it travels farther horizontally for each unit of vertical bounce than does the backspin ball (see Figure 1). "

However, this is unclear to me because "speed" can be a combination of the speed at which the ball is falling and the speed at which it is moving horizontally. What is not clear to me is what happens to a ball dropped from the same height that is not spinning at all vs one that is spinning. Assume no horizontal motion. Will the spinning ball bounce as high? I would assume not, but I may be wrong - again...

#### Born_to_slice

##### Professional
Top spin balls bouncing higher are due to trajectory. More loopy it is the higher it will bounce. Subtle low ball with top spin will shoot towards the ground faster than a flat one. Obviously we can't achieve loopy trajectory with a flat ball, but say we launch it from the apex of a loopy top spin trajectory it would bounce higher if hit with same force.

#### Gary Duane

##### G.O.A.T.
Yes, but only if the trajectory of the ball is the same.

Imparting those spins leads to different trajectories leaving the racquet for a start, but also a heavily spun topspin shot can be travelling close to vertically prior to the bounce as the affect of spin and friction with the air (the Magnus Effect) pushes the ball downwards.
Yup. The bottom line is that you can hit a topspin shot way higher over the net at a fast speed and have it drop, while a slice can actually defy gravity for a bit, so the trajectories will never be the same.

#### Gary Duane

##### G.O.A.T.
Top spin balls bouncing higher are due to trajectory. More loopy it is the higher it will bounce. Subtle low ball with top spin will shoot towards the ground faster than a flat one. Obviously we can't achieve loopy trajectory with a flat ball, but say we launch it from the apex of a loopy top spin trajectory it would bounce higher if hit with same force.
I think we all know this just from experience without understand why. What is behind all this? It's actually about tennis itself, not numbers. I want to know why Nadal was able to win 51% of his return games on clay in 2008. I want to know how the bounce and speed on clay can be so different as to let players - and not just Rafa - defend so much better on clay.

There is all this talk about grass playing like clay, or slow HC playing like clay. But if that is true, we should see clay court players having the same results on these supposedly ultra slow court HC surfaces.

We all know that red clay plays the slowest. But is there something we don't see that players experience? How much difference does the sliding change movement? Is the movement itself as big a factor as the bounce and speed of the courts? How much is speed confused with bounce? Is there something else going on about the movement of the ball on clay that we miss? Or that only experienced players sense, without being able to put it into words?

You would think that if a HC bounces as high as red clay and there is enough grit on the HC to grip the ball the same amount, you would end up with similar results in return and service stats. I don't ever see stats that show these two factors separately. If, for instance, a supposedly slow HC gives as high a bounce as clay, and some seem to get pretty close, then the difference in results should be mainly in the grit. The grit is then going to determine what most people think of as "speed", and that "speed" is going to be dependent on friction, I think. So the next question is whether or not you can make a high bouncing HC grip as much as red clay. The answer may be that it is possible, but the result might be like sand paper, and I would imagine such a surface would be awful on the body if you ever fell. And of course instead of skidding, as HC players now do, most of that would stop.

That's my question. I wish there were a measurement of court friction, how much the various courts grab the ball. Years ago sometimes players played on wood, and I would imagine on that surface, even if you got a fairly high bounce, the ball would shoot through like a rocket. Carpet I guess could be very variable according to the "weave" or something like that.

#### Born_to_slice

##### Professional
I think we all know this just from experience without understand why. What is behind all this? It's actually about tennis itself, not numbers. I want to know why Nadal was able to win 51% of his return games on clay in 2008. I want to know how the bounce and speed on clay can be so different as to let players - and not just Rafa - defend so much better on clay.

There is all this talk about grass playing like clay, or slow HC playing like clay. But if that is true, we should see clay court players having the same results on these supposedly ultra slow court HC surfaces.

We all know that red clay plays the slowest. But is there something we don't see that players experience? How much difference does the sliding change movement? Is the movement itself as big a factor as the bounce and speed of the courts? How much is speed confused with bounce? Is there something else going on about the movement of the ball on clay that we miss? Or that only experienced players sense, without being able to put it into words?

You would think that if a HC bounces as high as red clay and there is enough grit on the HC to grip the ball the same amount, you would end up with similar results in return and service stats. I don't ever see stats that show these two factors separately. If, for instance, a supposedly slow HC gives as high a bounce as clay, and some seem to get pretty close, then the difference in results should be mainly in the grit. The grit is then going to determine what most people think of as "speed", and that "speed" is going to be dependent on friction, I think. So the next question is whether or not you can make a high bouncing HC grip as much as red clay. The answer may be that it is possible, but the result might be like sand paper, and I would imagine such a surface would be awful on the body if you ever fell. And of course instead of skidding, as HC players now do, most of that would stop.

That's my question. I wish there were a measurement of court friction, how much the various courts grab the ball. Years ago sometimes players played on wood, and I would imagine on that surface, even if you got a fairly high bounce, the ball would shoot through like a rocket. Carpet I guess could be very variable according to the "weave" or something like that.
http://www.tennistopten.com/articles/surfaces.pdf
Clay is the slowest/highest bouncing surface. It is also the most uneven, thus favors the playstyle with most margin for errors - heavy top spin. You can make it awkward for your opponent by playing very safe. It also makes the serve least potent than on other surfaces and voila - Nadal excels on it. His least preferred courts is indoor hc which is not affected by outside influences and lends itself to the more textbook precision playstyles.

#### Gary Duane

##### G.O.A.T.
http://www.tennistopten.com/articles/surfaces.pdf
Clay is the slowest/highest bouncing surface. It is also the most uneven, thus favors the playstyle with most margin for errors - heavy top spin. You can make it awkward for your opponent by playing very safe. It also makes the serve least potent than on other surfaces and voila - Nadal excels on it. His least preferred courts is indoor hc which is not affected by outside influences and lends itself to the more textbook precision playstyles.
Certainly less even than any HC, but grass? I think that's not true. I never played on grass, but with the low bounce and so on it has to be the most uncertain.

But I think the main factor is time. When the ball does not move forward as fast, you have more time to time the ball's horizontal movement. Then if the ball bounces high it's easier to adjust the point you are hitting the ball at (height) by moving back exactly where you want to be to get the ball at a comfortable height. But when the ball comes skidding through positioning is harder and it's easier to get the ball a bit too early or late. Then when you add to that a low bounce - like grass or an indoor court where the ball does not come up much - then you have the least amount of time and everything is more about a super compact swing and reactions.

So I think the main factor for Nadal is grit. If they made the USO into sandpaper, it might be horrible on his knees, and he could not slide, but he'd probably time the ball better from way back. I think that's why he has done so badly indoors - low bounce to start with. I'd love to know both at Cincy. They say it's fast. But I'd like to know about the bounce and grit. Maybe they keep those courts pretty slick. I don't know about the bounce. Probably a bit lower.

#### Jaitock1991

##### Hall of Fame
Top spin balls bouncing higher are due to trajectory. More loopy it is the higher it will bounce. Subtle low ball with top spin will shoot towards the ground faster than a flat one. Obviously we can't achieve loopy trajectory with a flat ball, but say we launch it from the apex of a loopy top spin trajectory it would bounce higher if hit with same force.
I wonder if this is the reason why Fed usually put a lot of sidespin on the ball rather than backspin on his short slices back in the day.

#### Born_to_slice

##### Professional
Certainly less even than any HC, but grass? I think that's not true. I never played on grass, but with the low bounce and so on it has to be the most uncertain.

But I think the main factor is time. When the ball does not move forward as fast, you have more time to time the ball's horizontal movement. Then if the ball bounces high it's easier to adjust the point you are hitting the ball at (height) by moving back exactly where you want to be to get the ball at a comfortable height. But when the ball comes skidding through positioning is harder and it's easier to get the ball a bit too early or late. Then when you add to that a low bounce - like grass or an indoor court where the ball does not come up much - then you have the least amount of time and everything is more about a super compact swing and reactions.

So I think the main factor for Nadal is grit. If they made the USO into sandpaper, it might be horrible on his knees, and he could not slide, but he'd probably time the ball better from way back. I think that's why he has done so badly indoors - low bounce to start with. I'd love to know both at Cincy. They say it's fast. But I'd like to know about the bounce and grit. Maybe they keep those courts pretty slick. I don't know about the bounce. Probably a bit lower.
Grass has low bounce, so that doesn't suit Nadal in the fist place. I've rarely seen court play so uneven like Rome this year during Diego-Novak SF. I've never seen anything like that on grass, even in small tournaments. Also lines are nightmare on clay courts, being made from different material (some kind of Vinyl/plastic), so even when the court is perfect bounce isn't the same like on the rest of the court. If court is in bad shape, there's almost no way to predict how ball will bounce, especially if it catches the line. There's no higher maintenance courts than clay. For Nadal, I think he needs a combination of both slowness of court and high bounce to really excel on it. His physicality and grit is diminished now and I don't think he can win outside of his favorite surface without a help of a easy draw. Maybe even in RG. Wonder how'd he do with Thiem's or Novak's draw from this year, especially playing 4 days in a row. Even got lucky with that wind against Federer imo.
I wonder if this is the reason why Fed usually put a lot of sidespin on the ball rather than backspin on his short slices back in the day.
I guess it can depend from where you're hitting it. Slice doesn't handle heavy top spin that well tho. I like how he hits the half volleys and doesn't back up now against Nadal.

Last edited:

#### Shaolin

##### G.O.A.T.
Before you conclude that this is a "Captain Obvious" question, check your perception.

Think about a ball that is hit 70 mph or more, backhand or forehand, then picture that ball hit with a lot of spin. Then picture that ball spinning with 5000 rpms. 5000 is incredibly high, much faster than most shots, but let's use that as a kind of limit.

What does that ball do as it bounces? Does it pick up more spin, lose spin, or stay about the same?

All my life I've had a perception that high topspin grabs the court and increases the forward pace of the ball. Same thing in table tennis. My impression was that topspin makes the ball take off, leap forward. It takes away from your time. It's like the ball gets to you too soon. In tennis it's like the ball is suddenly past you. You're swinging late.

But is this true?

If this video is correct, a couple things stick out. First of all, on the HC shown the ball is actually move at 33 mph after the bounce and 27 mph on clay. That's a lot slower than I had pictured. Obviously the ball loses speed from the time it is hit, but it loses more speed than I had realized after the bounce.

Even so, is the ball ever really spinning faster than it is moving horizontally?

What do you think? I believe I have an answer, and the answer is not what I expected.
I played a guy recently that was #1 in Brazil as a junior with mega topspin....not 5,000 rpm but it was significant. The ball really lurches forward after it hits and then jumps away. Feels like it actually picks up speed when it hits the court(doubt it actually does but that's how it feels).

#### travlerajm

##### Legend
Before you conclude that this is a "Captain Obvious" question, check your perception.

Think about a ball that is hit 70 mph or more, backhand or forehand, then picture that ball hit with a lot of spin. Then picture that ball spinning with 5000 rpms. 5000 is incredibly high, much faster than most shots, but let's use that as a kind of limit.

What does that ball do as it bounces? Does it pick up more spin, lose spin, or stay about the same?

All my life I've had a perception that high topspin grabs the court and increases the forward pace of the ball. Same thing in table tennis. My impression was that topspin makes the ball take off, leap forward. It takes away from your time. It's like the ball gets to you too soon. In tennis it's like the ball is suddenly past you. You're swinging late.

But is this true?

If this video is correct, a couple things stick out. First of all, on the HC shown the ball is actually move at 33 mph after the bounce and 27 mph on clay. That's a lot slower than I had pictured. Obviously the ball loses speed from the time it is hit, but it loses more speed than I had realized after the bounce.

Even so, is the ball ever really spinning faster than it is moving horizontally?

What do you think? I believe I have an answer, and the answer is not what I expected.
I think the answer is... it depends. When I hit really heavy high-speed serves with a really spinny string setup, sometimes, but not always the topspin rpm is enough to make the ball shoot forward fast enough that it certainly appears that the ball is gaining forward velocity after the bounce. The bounce angle is very low compared to the steep downward incident angle. I think it’s because the ball’s surface velocity is just right within the window to create rolling friction.

But ordinarily, with topspin groundstrokes, or with topspin serves under most conditions, the bounce is mostly sliding friction, which slows the ball down a lot and creates a higher bounce angle than the incident angle.

Last edited:

#### moonballs

##### Hall of Fame
All I know is the top spin makes a huge difference. For example shoulder height ball at base line. If there is no top spin I can unload a forehand to one of the corners. If there is some top spin the bounce is different enough and I have to worry more about controlling it.

#### travlerajm

##### Legend
All I know is the top spin makes a huge difference. For example shoulder height ball at base line. If there is no top spin I can unload a forehand to one of the corners. If there is some top spin the bounce is different enough and I have to worry more about controlling it.
If you play with tighter strings then the incoming spin matters less.

#### blablavla

##### Professional
If you play with tighter strings then the incoming spin matters less.
only if you know how to hit a shoulder high ball, or how to take the ball on the rise

#### SeeItHitIt

##### Semi-Pro
Interesting topic, thanks for the provocative post.

Kind of off the subject and not to hijack, but Hawkeye was mentioned. It’s always been a pet peeve criticism of Hawkeye that every shot is assumed to have the same ball contact patch/shape (elongated and on its shot direction axis)...ball rotation, trajectory and speed seem to be ignored (unless it’s baked into an algorithm).

#### moonballs

##### Hall of Fame
If you play with tighter strings then the incoming spin matters less.
Yes I will definitely try up the tension. The other cause is the bounce is indeed different with top spin.

##### Hall of Fame
Before you conclude that this is a "Captain Obvious" question, check your perception.

Think about a ball that is hit 70 mph or more, backhand or forehand, then picture that ball hit with a lot of spin. Then picture that ball spinning with 5000 rpms. 5000 is incredibly high, much faster than most shots, but let's use that as a kind of limit.

What does that ball do as it bounces? Does it pick up more spin, lose spin, or stay about the same?

All my life I've had a perception that high topspin grabs the court and increases the forward pace of the ball. Same thing in table tennis. My impression was that topspin makes the ball take off, leap forward. It takes away from your time. It's like the ball gets to you too soon. In tennis it's like the ball is suddenly past you. You're swinging late.

But is this true?

If this video is correct, a couple things stick out. First of all, on the HC shown the ball is actually move at 33 mph after the bounce and 27 mph on clay. That's a lot slower than I had pictured. Obviously the ball loses speed from the time it is hit, but it loses more speed than I had realized after the bounce.

Even so, is the ball ever really spinning faster than it is moving horizontally?

What do you think? I believe I have an answer, and the answer is not what I expected.
There are different types of topspin. Some jump out, some jump up, its based on the arc of the shot. Imagine your trying to make a moonball bounce over the back fence, as you can imagine you need a certain amount of arc height to achieve a high bounce height.

A 70mph flat shot is much different than topspin at 5k rpm.

#### Dondon

##### Semi-Pro
When the spin touches the string

Gut will be broken like a chainsaw on tree trunks

Dats where it hurts

#### Russeljones

##### G.O.A.T.
Before you conclude that this is a "Captain Obvious" question, check your perception.

Think about a ball that is hit 70 mph or more, backhand or forehand, then picture that ball hit with a lot of spin. Then picture that ball spinning with 5000 rpms. 5000 is incredibly high, much faster than most shots, but let's use that as a kind of limit.

What does that ball do as it bounces? Does it pick up more spin, lose spin, or stay about the same?

All my life I've had a perception that high topspin grabs the court and increases the forward pace of the ball. Same thing in table tennis. My impression was that topspin makes the ball take off, leap forward. It takes away from your time. It's like the ball gets to you too soon. In tennis it's like the ball is suddenly past you. You're swinging late.

But is this true?

If this video is correct, a couple things stick out. First of all, on the HC shown the ball is actually move at 33 mph after the bounce and 27 mph on clay. That's a lot slower than I had pictured. Obviously the ball loses speed from the time it is hit, but it loses more speed than I had realized after the bounce.

Even so, is the ball ever really spinning faster than it is moving horizontally?

What do you think? I believe I have an answer, and the answer is not what I expected.
Spin (as in 12 o'clock top spin) should impact horizontal momentum.

#### Gary Duane

##### G.O.A.T.
There are different types of topspin.
I'm sure you mean that there are different kinds of topspin shots.

Here are the factors that matter:

The height of the trajectory (which determines how far the ball will fall and pick up speed for the bounce.)
The angle with which the ball strikes the court (determines the angle of the bounce.)
Spin (changes the bounce by adding to or subtracting from forward movement or causing the ball to move sideways.)

For topspin here is what we care about: if the ball is spinning faster than the ball is moving forward, the spin will add to the forward motion. At the same speed the spin will not add to or subtract from forward motion. If the spin is slower than the forward motion, it will subtract from that forward motion.

What we are discussing - or at least I am discussing - is how the grittiness of a court changes forward speed. This is a completely different factor from the height of the bounce, but these two factors always combine together for overall results

Bottom line: since the forward spin of a topspin shot is almost always slower than the speed the ball is moving forward, any increase in grittiness (friction) slows most shots down. So by adding grit AND increasing the height of the bounce you get the kind of results talked about at the USO, at least in the past. The bounce itself can be changed both by making the surface harder and/or making balls more lively.

##### Hall of Fame
I'm sure you mean that there are different kinds of topspin shots.

Here are the factors that matter:

The height of the trajectory (which determines how far the ball will fall and pick up speed for the bounce.)
The angle with which the ball strikes the court (determines the angle of the bounce.)
Spin (changes the bounce by adding to or subtracting from forward movement or causing the ball to move sideways.)

For topspin here is what we care about: if the ball is spinning faster than the ball is moving forward, the spin will add to the forward motion. At the same speed the spin will not add to or subtract from forward motion. If the spin is slower than the forward motion, it will subtract from that forward motion.

What we are discussing - or at least I am discussing - is how the grittiness of a court changes forward speed. This is a completely different factor from the height of the bounce, but these two factors always combine together for overall results

Bottom line: since the forward spin of a topspin shot is almost always slower than the speed the ball is moving forward, any increase in grittiness (friction) slows most shots down. So by adding grit AND increasing the height of the bounce you get the kind of results talked about at the USO, at least in the past. The bounce itself can be changed both by making the surface harder and/or making balls more lively.
X steals spin from Y
Y steals mph from X

Just look at trajectory. Thats what makes feds topspin impressive, it has lower net clearance but a similar height. Someone posted a chart a while back that explains.

Slower surfaces compliment the height of the bounce, not the speed of the bounce. Flat is the fastest shot because it has the least resistance.

Do a comparison to the speed of a flat fh after the bounce vs a topspin. Not saying top is bad, just a different type of weapon.

Its why ppl hit flat first serves and overheads. Topspin is much safer as we see on the 2nd serve, same applies to groundies

#### Gary Duane

##### G.O.A.T.
X steals spin from Y
Y steals mph from X

Just look at trajectory. Thats what makes feds topspin impressive, it has lower net clearance but a similar height. Someone posted a chart a while back that explains.

Slower surfaces compliment the height of the bounce, not the speed of the bounce. Flat is the fastest shot because it has the least resistance.

Do a comparison to the speed of a flat fh after the bounce vs a topspin. Not saying top is bad, just a different type of weapon.

Its why ppl hit flat first serves and overheads. Topspin is much safer as we see on the 2nd serve, same applies to groundies
Your pointing out one set of factors, and they are important. There are two different things going on. One is the time it takes for the ball to get from point A to point B, assuming both shots have the same trajectory. And to land at the same point, they will have the same trajectory. This is to the exact moment before the ball bounces.

The other factor is how fast the ball takes off after bouncing. Those two factors can combine in any way. You can have no topspin, a little a lot, and you can even have a small amount of backspin (Connors and a few others, also the Rosewall backhand.)

This is why the amount of grit is so important. The same shot will arrive to the same place in the same amount of time, with the same speed, but the gritty court will immediately pull pace off the ball unless it is spinning as fast as it is moving forward.

So let's say you are right that the flat shot travels the fastest because it takes a more direct path, less arc - which is logical. You then have to balance against that how much more risky it is to hit that shot flat, with less net clearance.

On a very smooth surface that flat shot if it clears the net will penetrate more or move through faster because the surface will not pull speed off the ball as it bounces. The heavier the topspin, the less the surface is going to change the speed. If you combine a very smooth surface with a low bouncing one you get the very fastest court possible. Very gritty and high bounce is red clay.

Last edited:

##### Hall of Fame
Your pointing out one set of factors, and they are important. There are two different things going on. One is the time it takes for the ball to get from point A to point B, assuming both shots have the same trajectory. And to land at the same point, they will have the same trajectory. This is to the exact moment before the ball bounces.

The other factor is how fast the ball takes off after bouncing. Those two factors can combine in any way. You can have no topspin, a little a lot, and you can even have a small amount of backspin (Connors and a few others, also the Rosewall backhand.)

This is why the amount of grit is so important. The same shot will arrive to the same place in the same amount of time, with the same speed, but the gritty court will immediately pull pace off the ball unless it is spinning as fast as it is moving forward.

So let's say you are right that the flat shot travels the fastest because it takes a more direct path, less arch - which is logical. You then have to balance against that how much more risky it is to hit that shot flat, with less net clearance.

On a very smooth surface that flat shot if it clears the net will penetrate more or move through faster because the surface will not pull speed off the ball as it bounces. The heavier the topspin, the less the surface is going to change the speed. If you combine a very smooth surface with a low bouncing one you get the very fastest court possible. Very gritty and high bounce is red clay.
I once played on a basketball court that was converted to tennis (polished wood). Flat shots are deadly, they increase in speed after the bounce. Also remember the bounce is around half the height of peak arc, makes it even worse.

Players are now using more arc on their shot because the surface caters to it. You get much more benefit from height than you do speed. Makes tennis a fitness battle at the pro lvl

#### Gary Duane

##### G.O.A.T.
I once played on a basketball court that was converted to tennis (polished wood). Flat shots are deadly, they increase in speed after the bounce. Also remember the bounce is around half the height of peak arc, makes it even worse.

Players are now using more arc on their shot because the surface caters to it. You get much more benefit from height than you do speed. Makes tennis a fitness battle at the pro lvl
A flat shot can't pick up speed after bouncing. That would break the laws of physics.

What happens is that the body/eyes are expecting things to happen. Your brain knows that a flat ball coming at you at X speed is only supposed to move "so fast" after it bounces, so on a very smooth surface it's a shock to find it moving way faster than you are used to. This is also what makes a topspin shot seem to jump forward at you, taking time. Most of the time it too is "braking" due to friction, but much less so than other shots. Your mind is continually monitoring how the ball reacts after bouncing, and if your opponent is hitting different amounts of spin, you get used to slices checking up. You have to move close to the bounce. Flat shots come through faster. Heavy topspin slows the least after bouncing, so it seems to jump right into you. Heavy topspin with a high bounce is most uncomfortable because of where you have to play the ball.

It's all about the relativity of the shots. If it comes at you faster, that's all you care about. If you lose time, you have to figure that out.

When we were young my brother and I used to bike to a church that had really great, sidewalks, concrete, that were in incredibly smooth. We took our skates there. We also had an outdoor skating rink that was - get this - concrete! You could fall on that without really skinning your knees or elbows because the surface was so smooth. Obviously very hard. So if players played on such a surface everything would shoot through, like your wooden surface, but a higher bounce. It might be fun if you could keep from breaking your neck.

I've never seen the courts at places like the USO, but I'm imagining they must be very gritty, like sandpaper but with larger particles. Most be pure hell to take a tumble on...

##### Hall of Fame
A flat shot can't pick up speed after bouncing. That would break the laws of physics.
The bounce is half the peak, so X is increased on a surface with no resistance. Its an extreme example, i remember someone doing it on ice.

Brb

#### Gary Duane

##### G.O.A.T.
The bounce is half the peak, so X is increased on a surface with no resistance. Its an extreme example, i remember someone doing it on ice.

Brb
I don't know what X is. As for the bounce, we know that the supposed specs for tennis balls is a bounce of 53-58 inches from a height of 100 feet. But I did not find out what that test uses to drop the ball on.

I'd love to know how that changes from clay to concrete to asphalt to the surfaces on HC slams to grass. But it would be interesting to know.

Not sure why you say speed is increased on a surface with no resistance. That makes no sense.

##### Hall of Fame
Basic x/y chart. X = speed of the ball, Y= height. Image zero being the net (the numbers on x dont apply here unless wanna do distance) and draw a line. Will be a slight bell curve because the ball has to go above the net with safe clearence, what you gain with top.

Just flip the script, if a fast surface does this for a flat ball, a rigid surface must do the same for spin when you factor in the established variable.

Hardcourts are very good now, most are similar to the usopen (common like hdtvs now). Very slow and eat up your shoes. A new hardcourt is my fav surface, plays like clay with a consistent bounce

"Not sure why you say speed is increased on a surface with no resistance. That makes no sense."

With no resistance the ball doesnt lose speed on bounce, increased was wrong. Just felt like it in comparison i guess

#### Gary Duane

##### G.O.A.T.
Basic x/y chart. X = speed of the ball, Y= height. Image zero being the net (the numbers on x dont apply here unless wanna do distance) and draw a line. Will be a slight bell curve because the ball has to go above the net with safe clearence, what you gain with top.

Just flip the script, if a fast surface does this for a flat ball, a rigid surface must do the same for spin when you factor in the established variable.

Hardcourts are very good now, most are similar to the usopen (common like hdtvs now). Very slow and eat up your shoes. A new hardcourt is my fav surface, plays like clay with a consistent bounce

"Not sure why you say speed is increased on a surface with no resistance. That makes no sense."

With no resistance the ball doesnt lose speed on bounce, increased was wrong. Just felt like it in comparison i guess
There you go. Just like topspin does not make the ball increase in speed, just decreases how much speed the ball loses.

Not sure if I explained this, but I was a bit shocked when I found out that 5000 rpms is only 39 mph. I was also shocked to find out that the speed of a pretty fast shot is below 40 mph after the bounce and under 30 on clay. There are a lot of things that seem crazy but are true. The friction of air takes a huge amount of pace away by the time the ball gets over the net and bounces, then friction takes away more. Something coming at you at around 35 mph after the bounce is pretty damned fast when you are in front of it, especially when the bounce is low. You have so little time to react to any change, and that's what makes grass, even today's grass, so "fast".

By the way, I wonder how much the new grass has anything to do with anything? Seems like the major change in bounce comes from how they plant the grass!

#### FiReFTW

##### Legend
So much confusion but its so simple.

The actual ball speed slows down after bounce.

The more topspin the less it slows down however after bounce.

You however see the ball speed up after bounce the more heavy spin it has.

Thats because two reasons that are connected to each other:

1. The more spin the more speed the ball retains after the bounce (even tho it loses some) so it comes into you faster compared to a ball with little spin which loses more speed after bounce so comes into you slower

2. The more spin the more the ball dips down into the court before bounce, and the more the ball dips down the more its trajectory is going down instead of towards you, so even tho the speed may be the same it appears to slow down alot prior to bounce because its traveling more down into the court

So more spin=

More dip down prior to bounce which looks as if the ball slows down alot even tho it doesnt

Less speed loss after bounce so the ball gets to you faster after bounce compared to little spin ball

So its quite obvious why it appears like the heavy spin ball shoots into you and picks up speed after bounce.

It doesnt actually, tho if we look at only horizontal speed and not actual ball speed then it indeed would see the horizontal movement of the ball slow down alot aa the ball dips down more and then speed up alot as it bounces from the court

#### Enga

##### Hall of Fame
The spin adds centripetal force, making the ball direct its momentum towards the ground after arcing. So its momentum will be on a more vertical axis. This will happen no matter what the original angle the ball was hit at. So even if say Federer hit the ball with a flat horizontal trajectory with a lot of force, if he added a lot of topspin to it as well centripetal force will make the ball drop faster vertically, which in turn will make it bouncer upwards more.

Theres also a forward motion that the ball can take after the bounce. Its largely determined by the amount of grip the ball can get on the surface when it bounces off the ground, and the amount of spin. The ball can be thought of as a tire in that sense. I think it only really matters on a surface with a lot of grip or "friction", like clay or a sandy hardcourt.

#### Gary Duane

##### G.O.A.T.
So much confusion but its so simple.

The actual ball speed slows down after bounce.

The more topspin the less it slows down however after bounce.

You however see the ball speed up after bounce the more heavy spin it has.

Thats because two reasons that are connected to each other:

1. The more spin the more speed the ball retains after the bounce (even tho it loses some) so it comes into you faster compared to a ball with little spin which loses more speed after bounce so comes into you slower

2. The more spin the more the ball dips down into the court before bounce, and the more the ball dips down the more its trajectory is going down instead of towards you, so even tho the speed may be the same it appears to slow down alot prior to bounce because its traveling more down into the court

So more spin=

More dip down prior to bounce which looks as if the ball slows down alot even tho it doesnt

Less speed loss after bounce so the ball gets to you faster after bounce compared to little spin ball

So its quite obvious why it appears like the heavy spin ball shoots into you and picks up speed after bounce.

It doesnt actually, tho if we look at only horizontal speed and not actual ball speed then it indeed would see the horizontal movement of the ball slow down alot aa the ball dips down more and then speed up alot as it bounces from the court
It's all a series of optical illusions. Without modern equipment to measure what is happening we'd just know that topspin rotates towards us, and that it makes the ball dive down. Then we know that different balls rotate differently after they bounce, but what I'd love so see are slow motion videos of various shots as the land, to watch exactly how the balls rotate immediately after bouncing. What happens, for instance, with a slice backhand that is spinning as fast backwards as it is moving forward in its path? Will it still be rotating backwards? Or close to zero spin?

When we see a topspin shot coming at us, we see it rotating forward after the bounce, but we have no idea how fast that is in comparison to what it was doing right before the bounce unless we have equipment to measure it. It happens too fast.

Decades ago people used to say to come over the ball on a topspin shot. The idea was that the wrist rotated, and that put spin on the ball. Today we know that is totally false.

Another mistake: people used to say that servers like Tanner hit the ball on the way up. Eventually slo motion proved that at most a few servers hit the ball just as it reaches its apex, and even for those players, guys like Dogopolov and Kyrgios, even they hit the ball after it drops just a tiny bit.

Everything looks different in slo-mo, and it's strange to think that everything we see that way was unknown a century ago, and less.