This may be sacrelige, but why do people care so much about spin?

[Fugazi]

You have to remember that always - all the time - all the objects have an external force applied to them, it is called gravity, topspin actually slow down the ball right before bouncing, the trajectory of the ball is not at constant speed, so I would say that it is not "crazy" to say that the ball could have a higher speed after bounce.

It's probably not often true, but if a really slow ball has, say, insane spin, then it's obvious that it'll be not only faster after the bounce compared to a similar shot without spin, but also faster than before the bounce.

 

[jmverdugo]

I am just going to say that it is way more complicated than an energy equation, you have to think about the air density, the RPM of the ball, the linear speed, then angle of incidence, the friction between the ball and the street, the material of the ball, the material of the court and many others variables, the best thinkg to do would be to put everything on a simulation software and see what happen.

For now I am going to say that "in my experience" if you hit with decent topspin the ball does seem to have a higher velocity after the bounce. It is not unusual to see people stopping their run thinking the are in position to hit the ball just to realize they cannot reach the ball after it bounces, or the delusion on their face when they are running and think they will catch the ball and then it outruns them after the bounce.

 

[dadozen]

You have to remember that always - all the time - all the objects have an external force applied to them, it is called gravity, topspin actually slow down the ball right before bouncing, the trajectory of the ball is not at constant speed, so I would say that it is not "crazy" to say that the ball could have a higher speed after bounce.

Ok, this will be my last post regarding this 'physics' subject:

Gravity is a constant force, which applies - as you correctly say - on all objects, all the time. It's vertical, so its implication is only on the vertical trajectory of the ball. Taht's exactly why the ball usually has an elyptical trajectory.

The gravity works by making the ball slowly lose speed up and then gain speed down. So it won't make the ball go faster horizontally.

As I said before, the different angle and trajectory the ball has in a spinny shot( comparing to a flat shot ) makes it feel heavier, thus making it seem faster after the bounce.

Well, if something is not clear yet, go search the web or read a book. I'm not a native english speaker so it's hard to explain all this, but this is the idea.

 

[jmverdugo]

Ok, this will be my last post regarding this 'physics' subject:

Gravity is a constant force, which applies - as you correctly say - on all objects, all the time. It's vertical, so its implication is only on the vertical trajectory of the ball. Taht's exactly why the ball usually has an elyptical trajectory.

The gravity works by making the ball slowly lose speed up and then gain speed down. So it won't make the ball go faster horizontally.

As I said before, the different angle and trajectory the ball has in a spinny shot( comparing to a flat shot ) makes it feel heavier, thus making it seem faster after the bounce.

Well, if something is not clear yet, go search the web or read a book. I'm not a native english speaker so it's hard to explain all this, but this is the idea.

You are funny, "heavier" is not a scientific term, I do not need to look a book or the web, I understand what you are saying but you are leaving out too many variables. Look I have some experience on this, things are way more complicated, for instance the ball has different heights before and after the bounce (potential energy), what happens with this energy after the bounce? I think that part of it is transformed in kinetic energy maybe?

Another thing, why the angle of the bounce is different before and after the bounce? I think we would have to study more the interaction between the ball and the ground having in mind the RPMs of the ball to really have an idea about this.

 

[sepidoel]

I completely agree with Fugazi. I'll go a little further with Fugazi's example: Imagine 2 balls free fall, ball F (for flat) without any spin and ball S (for spin) with spin (let's say with Nadal class of spin). Ball F will bounce back upward while ball S will bounce forward. It means ball S had the energy kept (within its spin) to "kick" forward, while F did not. The energy was provided before ball S touched the floor, without any more external force.

Another point of view. When a ball is hit flat it will only have forward force work on it (just ignore the other complicated forces). With topspin, the force worked on the ball is divided to forward force and upper force. Thus if the same amount of force are used on both strokes, the flat one will definitely have faster velocity.

What Fugazi keep repeating is if both strokes produce the same velocity that means there is more force worked on the topspin one compare to the flat one. That additional force kept as the spin will be converted as forward force when it touch the floor. Minus the friction with the floor (and other), the S ball will have a larger forward "kicking" force compared to the F ball. Even without proper calculation it makes a lot of sense that in that case ball S is faster after bouncing.

 

[dadozen]

You are funny, "heavier" is not a scientific term, I do not need to look a book or the web, I understand what you are saying but you are leaving out too many variables. Look I have some experience on this, things are way more complicated, for instance the ball has different heights before and after the bounce (potential energy), what happens with this energy after the bounce? I think that part of it is transformed in kinetic energy maybe?

Another thing, why the angle of the bounce is different before and after the bounce? I think we would have to study more the interaction between the ball and the ground having in mind the RPMs of the ball to really have an idea about this.

Since you're being sarcastic, I don't need to be as respectful as I feel I should be, but anyways:

I didn't use heavier as a scientific term. Where did you read that? I wrote the ball would feel heavier for the player.

The angle will be different before and after the bounce simply because the ball is rotating!!! Of course, the surface of the floor will basically tell you if the variance will be great or not, but the rotation of the ball causes the difference.

You don't need to apply that many variables on the equation since you can assume everything the same: the ball, the court, the players, the racquets, the strings, the weather, the altitude of the location. Simply eliminate all this of the equation. Since you have experience on this, how can you have that left behind?

Last thing: potential energy transforms into kinetic energy when the object changes heights, such as a rollercoaster. A ball bounces on the floor, and since potential energy only applies vertically, you can assume that all potential energy the ball had before bouncing is kept after it bounces - obviously, subtracting the % loss during the impact on the ground.

I completely agree with Fugazi. I'll go a little further with Fugazi's example: Imagine 2 balls free fall, ball F (for flat) without any spin and ball S (for spin) with spin (let's say with Nadal class of spin). Ball F will bounce back upward while ball S will bounce forward. It means ball S had the energy kept (within its spin) to "kick" forward, while F did not. The energy was provided before ball S touched the floor, without any more external force.

Another point of view. When a ball is hit flat it will only have forward force work on it (just ignore the other complicated forces). With topspin, the force worked on the ball is divided to forward force and upper force. Thus if the same amount of force are used on both strokes, the flat one will definitely have faster velocity.

What Fugazi keep repeating is if both strokes produce the same velocity that means there is more force worked on the topspin one compare to the flat one. That additional force kept as the spin will be converted as forward force when it touch the floor. Minus the friction with the floor (and other), the S ball will have a larger forward "kicking" force compared to the F ball. Even without proper calculation it makes a lot of sense that in that case ball S is faster after bouncing.

You completely misunderstand the concept of force in physics. The ball bounces forward because of the rotation applied on it, not because of energy within.

The only other thing you can assume on the equation is the air resistance, which will work much harder on the spinny ball, thus making it describe a different trajectory.

PV, sorry for writing so many off-topic posts. I'll be off this thread and leave it return to its original subject.

 

[Deleted member 120290]

All this physics talk is useless as is the 100 MPH heavy spin shot,, unless you are Nadal (100 MPH with massive spin) or Delpo (100+ MPH relatively flat.)

I don't know anyone in this world who can hit close to 100 with huge spin other than Nadal. So for the 99.999999999999% of the population, you are probably better off with Federeresque, Djokovicesque shots that have good amount of spin but still penetrate thru the court.

If I could play like Nadal, I'd be more interested in the physics behind hitting with massive spin vs. relatively flat. But obviously I can't and I doubt that he will be able to either in a couple of years. But Federer is still playing at the elite level at 30 with his smooth, efficient, moderate spin style.

 

[jmverdugo]

Since you're being sarcastic, I don't need to be as respectful as I feel I should be, but anyways:

I was not trying to be sarcastic, sorry about this.

I didn't use heavier as a scientific term. Where did you read that? I wrote the ball would feel heavier for the player.

Actually the ball will feel heavier because it jumps towards the player faster than expected, not the other way around. The ball do not seem faster because it feels heavier...

The angle will be different before and after the bounce simply because the ball is rotating!!! Of course, the surface of the floor will basically tell you if the variance will be great or not, but the rotation of the ball causes the difference.

You are correct on this one, I also believe that one of the reason the angle is different is because of the rotation of the ball, but I also think that the rotation helps to increase the linear speed of the ball after the bounce

You don't need to apply that many variables on the equation since you can assume everything the same: the ball, the court, the players, the racquets, the strings, the weather, the altitude of the location. Simply eliminate all this of the equation. Since you have experience on this, how can you have that left behind?

Everything is the same compared to what? My point is that the air friction is a force and you have to have it in mind, gravity is another force and you also need to have it in mind, the weight of the ball is another force, the friction between the ground and the ball is another force that you also need to have in mind, the material of the ball will affect the bounce for sure, a brick would not bounce as a tennis ball. You said that it is not possible for the ball to change speed because there is not a force to make it do that, I am trying to tell you that there are plenty of forces that could do it.

Last thing: potential energy transforms into kinetic energy when the object changes heights, such as a rollercoaster. A ball bounces on the floor, and since potential energy only applies vertically, you can assume that all potential energy the ball had before bouncing is kept after it bounces - obviously, subtracting the % loss during the impact on the ground.

Again you forgetting some stuff, first the ball will have different max heights before and after the bounce and while some of the initial potential energy will be transform in something else at the moment of the bounce some of it will also be transformed in kinetic energy for sure and some of it will be loss because of the friction with the air.

 

[jmverdugo]

You completely misunderstand the concept of force in physics. The ball bounces forward because of the rotation applied on it, not because of energy within.

Ok, this is really wrong, explain to me why a slice bounce forward then ...

 

[BigT]

At the beginner level, where it seems many of the posters here find themsleves (3.0-4.0), the next step after being able to hit the ball over the net, is to put some spin on the ball.

Almost everytime I hit with a 4.0 player I'll get 'oohs and aahs' about how much spin my shots have, and how they are so hard to handle and jumping off the court.
To my normal partners though, it is nothing special, as everyone at the 5.0+ level can handle it with no problems, and they can step in and take it early.
Not only that, but I feel that too much spin is often a liability. I often have to work much harder to construct a point, where as the flatter hitting players can finish a point in 2-3 shots.

 

[pro10is4life]

Being a current Mechanical Engineering student and having dynamics fresh in my mind, I can tell you that a 100mph topspin shot will have more velocity after bouncing than a 100mph flat shot. Though possible, I'm not saying the topspin shot increases velocity after bounce, I am saying it will lose less velocity than the flat shot.

Yes, with enough topspin, the ball CAN increase it's velocity after bouncing. I know someone was wondering where this external force comes from. This force is friction. Friction isn't only used to slow things down, it can also speed an object up. This can happen if the relative velocity of the ball (where it makes contact with the court) is greater than zero, and the rest of this paragraph talks about this case. This relative velocity can be found by taking the angular velocity of the ball * the radius of the ball - the velocity of the ball. With the frictional force in the direction of the balls velocity, and opposing the direction of the relative velocity of the contact point of the ball, it makes sense that the ball's translational velocity would increase while the angular velocity would decrease. This can also be shown in terms of energy, this explanation should be sufficient.

 

[Tennis Is Magic]

It feels heavier because the angle of incidence of the ball on the stringbed is different, thus producing a different reaction of the arm/racquet when blocking/hitting that specific ball shot. As you know, bloking a flat shot is different from blocking a spinny shot, and that' what produces the feeling that a spinny shot is heavier.

But the speed of the ball is the same. a 100mph shot is a 100mph shot, no more no less.

Physics says that no object can gain/have its speeds increased without any external force being applied.

No, topspin actually increases the wait of the ball. Weight is a function of mass times acceleration due to gravity. While a ball does not gain mass, the topspin creates an area of high pressure above the ball, increasing downward acceleration, thus, the ball is heavier.

 

[pro10is4life]

I should have been a little more detailed in my post above.


"This can happen if the relative velocity of the ball (where it makes contact with the court) with respect to the tennis court is greater than zero, and the rest of this paragraph talks about this case. This relative velocity can be found by taking the angular velocity of the ball * the radius of the ball - the horizontal velocity of the ball. With the frictional force in the direction of the balls horizontal velocity, and opposing the direction of the relative velocity of the contact point of the ball with respect to the court, it makes sense that the ball's translational velocity would increase while the angular velocity would decrease. This can also be shown in terms of energy, this explanation should be sufficient.

 

[Deleted member 120290]

At the beginner level, where it seems many of the posters here find themsleves (3.0-4.0), the next step after being able to hit the ball over the net, is to put some spin on the ball.

Almost everytime I hit with a 4.0 player I'll get 'oohs and aahs' about how much spin my shots have, and how they are so hard to handle and jumping off the court.
To my normal partners though, it is nothing special, as everyone at the 5.0+ level can handle it with no problems, and they can step in and take it early.
Not only that, but I feel that too much spin is often a liability. I often have to work much harder to construct a point, where as the flatter hitting players can finish a point in 2-3 shots.

Very good point. I hit with 3.5 - 5.5 as I am 4.5. When playing against 3.5 - 4.0 all I have to do is hit heavy FH all day to their BH and they have a hard time returning it even when the ball is hit right to them. 4.5 is where it seems to even out. Against 5.0+ unless you are hitting these very close to the baseline the topspin shots go right into the strike zone (5.0+ tend to be taller). They then just wait for the ball and wail on them.

Another good point is that it takes a LOT of energy to play with heavy topspin. If you are playing a weaker player and he's doing all the running, hitting 3-5 shots a point is no big deal. But if you are playing against an advanced player, hitting 8-20 massive topspin shots takes a lot out of you, esp. your legs. As I said before, anyone not named Nadal is better off with moderate topspin, using angles, varying spins and speed, and hitting thru the court (on hardcourt and grass anyway.)

 

[GrandIllusion]

I like my strings like I like my women...natural, easy on the arm, 16g...Wait...

 

[fgs]

since the days of björn borg spin (topspin) has become an essential part of playing tennis. it is normal that people care about spin for the reasons already mentioned several times in the course of this thread.
marketing has found a new buzz-word in order to sell, and that is "the monster spin-producing string". everybody wants spin, so we tell everybody that our product gives the most spin. the funniest thing about it is that this is something which we can't prove them wrong - if you got the technique, you will get your spin and so you end up thinking that the spin-string is allright. if you haven't got the technique they will always have the excuse that without technique you can't experience the spin enhancing properties of their strings. it's as stupid as it is funny.
i have played some "spinny" strings so far and am going to play some more, but i have not found the monster-spin string and i doubt i will. i do have a heavy spin producing technique and so far i can't see any reason why i should switch to any shaped/structured monster-spin string from my current round string.
i can't say that it it all hype, but i'm going to say that the most of it is hype.

 

[Xizel]

I realized spin-happy strings die fast, so I stopped caring.

 

[Deleted member 120290]

Well I can understand that tennis is a business so they have to market to maximize their sales. Borg and Nadal are once in a generation type of players. For 40 yo 4.5 hackers to believe they can play like them by using their strings/rackets/dampeners is a little more than delusional. But I guess we can all dream. But that is like suggesting a 5'2" woman that she can serve bombs like Isner if she buys his Prince racket.

 

[fgs]

marketing is more subtle nowadays - nobody tells you you can spin it like nadal. they just tell you that this string "produces" spin for nadal, hence it can produce spin for you too. it will not be nadal-like spin, it will just be spin - they are playing with your mind in a more subtle way than they did 10 years ago.

 

[pvaudio]

Wow you guys really pulled this off the tracks haha

 

[pvaudio]

Being a current Mechanical Engineering student and having dynamics fresh in my mind, I can tell you that a 100mph topspin shot will have more velocity after bouncing than a 100mph flat shot. Though possible, I'm not saying the topspin shot increases velocity after bounce, I am saying it will lose less velocity than the flat shot.

Yes, with enough topspin, the ball CAN increase it's velocity after bouncing. I know someone was wondering where this external force comes from. This force is friction. Friction isn't only used to slow things down, it can also speed an object up. This can happen if the relative velocity of the ball (where it makes contact with the court) is greater than zero, and the rest of this paragraph talks about this case. This relative velocity can be found by taking the angular velocity of the ball * the radius of the ball - the velocity of the ball. With the frictional force in the direction of the balls velocity, and opposing the direction of the relative velocity of the contact point of the ball, it makes sense that the ball's translational velocity would increase while the angular velocity would decrease. This can also be shown in terms of energy, this explanation should be sufficient.

Yes, I did say all of this already. Let's stay on topic instead of bringing up physics concepts which cannot be applied to the discussion at hand and yield a legitimate result. dadozen and I both already said the ball will retain more speed after bouncing, and that unless there is an obscene amount of spin OR the shot is hit in such a way that it is not moving in a direction very quickly that the spin on the ball can increase its speed after bouncing. As I said, this is only likely with a good topspin lob because any other ball will lose an obscene amount of pace since the ball is not hitting the court in an elastic fashion. Let's get back on topic and leave this alone.

And no, I do not use proper physics terminology on the forum since this is all conjecture and cannot be proven outside of a controlled experiment.

 

[Fugazi]

"You completely misunderstand the concept of force in physics. The ball bounces forward because of the rotation applied on it, not because of energy within."

I think that's what he meant...

 

[Fugazi]

Being a current Mechanical Engineering student and having dynamics fresh in my mind, I can tell you that a 100mph topspin shot will have more velocity after bouncing than a 100mph flat shot. Though possible, I'm not saying the topspin shot increases velocity after bounce, I am saying it will lose less velocity than the flat shot.

Yes, with enough topspin, the ball CAN increase it's velocity after bouncing. I know someone was wondering where this external force comes from. This force is friction. Friction isn't only used to slow things down, it can also speed an object up. This can happen if the relative velocity of the ball (where it makes contact with the court) is greater than zero, and the rest of this paragraph talks about this case. This relative velocity can be found by taking the angular velocity of the ball * the radius of the ball - the velocity of the ball. With the frictional force in the direction of the balls velocity, and opposing the direction of the relative velocity of the contact point of the ball, it makes sense that the ball's translational velocity would increase while the angular velocity would decrease. This can also be shown in terms of energy, this explanation should be sufficient.

Thanks for that!