If this eventuates they will need to redefine a forward pass me thinks. Anyone moving at a pace and throws a flat pass will effectively be throwing a forward pass, it's psychics. The ball will travel forward as a result, not relative to themselves or their team mates, relative to the ground. I can see this going very wrong.....
Just revisiting this old chestnut...
To answer your question @mike there is no need to redefine anything. The ball speed would be constantly monitored, if it slows that's a fair pass, if the ball speed increases that's a forward pass. And it's in real time so it can be immediately ruled on just as if the ref blew the whistle.
I know many aren't a fan but for mine if they get the ball tech right it solves a heap of problems... including whether the ball is actually knocked on or not. But it will need to be extremely accurate to do this.
What if a player is accelerating as he passes the ball?
I don't think the physics of what barra said works at all - I'm going to guess that many, perhaps most passes speed up compared to being held by a runner, because the passer supplies power to make the ball move.
To think of it another way - most passes should cover distance much more quickly than if the ball was being carried by a runner, which means they must by definition move faster. So picture, for instance, a quality cut-out pass that covers half the field - simply no way the ball can be carried that quickly, and actually most big passes involve the passer slowing down, so they have more wind-up power and control.
Last article I saw the NRL were working with a type of Hawkeye-like technology that could track the relative ball position on the field. They weren't judging forward passes by straight lines on the field, because as noted, passes from a runner will travel forward relative to the point the ball was release. Rather, the technology they were looking at was basically measuring whether passes left the player's hands in a backwards direction (or not) - which is the law of the pass.
I assume it's fairly complicated to measure the physics and why they need some kind of ball chip and multi-angle system to measure ball movement relative to the camera. Probably also in a fashion similar to how cricket cams predict ball trajectory for LBW referrals.
Annesley did say at the time - if the technology could not get it right near 100% of the time then there was no point introducing it.
The physics works perfectly, if you only think in one dimension, up and down the field. Hypothetically, if the technology only measured the balls speed in one axis it would work in every case and scenario and the ball "floating" forward problem is taken out of it. If the balls velocity increases towards the opposition line, its a forward pass, if it stays the same or slows its legal.
I have never thought of it that way, I always assume it was some sort of ball tracking or "hawk eye" thing, but that system makes a lot of sense and would work in every situation.
But it wouldn't work in every situation as there are other variables in play. If a player is accelerating and passes the ball backwards it is still possible for the ball to go backwards out of the hands and still increase it's forward speed..
That is without going into how a change of direction of a player can increase the balls forward speed.
No it cant. The only way the ball can increase its speed (accelerate) is if a force is acting on it. Once a force is not acting on it, there is no acceleration. its been this way since Newton was a boy.
In your example, imagine JAC sprints from a dead start to near top speed, accelerating very fast and at the point he was going to pass, just let go of the ball. From dead stop the ball accelerates at the same rate as JAC. At the point JAC lets go of the ball, if we forget about air friction and wind etc) the ball would stop accelerating (there is no longer a force acting on it, JACs legs) and the ball would continue on at the same velocity as when JAC let go of the ball (it would obviously slow very slightly due to air and wind and then obviously slow when it hits the ground).
In the same situation, if JAC passes it instead of letting go of it, if the velocity of the ball in the north south axis increases (accelerates) this means and additional force has been applied to the ball in that direction, a literal forward pass. If not, its legal.
F=ma is only true in a straight line. The more precise way of expressing the equation is (see diagram) Where F and a have direction.
F=ma is only true in a straight line. The more precise way of expressing the equation is (see diagram) Where F and a have direction.
The issue is you need to understand vectors and vector arithmetic to get the true direction of the ball. Also what direction is the ball in relation to?That’s why I believe we need a more precise definition of a forward pass.
Few things Mike. F=Ma is true in all circumstances, everywhere, in all corners of the universe since the big bang. F=Ma is not only true in a straight line. F, M and a are all vectors and therefore the direction of each is a factor of each together. The direction is part of the vector.
The issue isnt that I need to understand vectors and vector arithmetic, I passed that section (the first week) of my BSc at USyd. The direction of the ball is completely irrelevant, the direction of the F and the a, relative to the north south axis (toward the opponents goal line) is all that matters and that is literally the existing definition of a forward pass.
If this eventuates they will need to redefine a forward pass me thinks. Anyone moving at a pace and throws a flat pass will effectively be throwing a forward pass, it's psychics. The ball will travel forward as a result, not relative to themselves or their team mates, relative to the ground. I can see this going very wrong.....
Just revisiting this old chestnut...
To answer your question @mike there is no need to redefine anything. The ball speed would be constantly monitored, if it slows that's a fair pass, if the ball speed increases that's a forward pass. And it's in real time so it can be immediately ruled on just as if the ref blew the whistle.
I know many aren't a fan but for mine if they get the ball tech right it solves a heap of problems... including whether the ball is actually knocked on or not. But it will need to be extremely accurate to do this.
What if a player is accelerating as he passes the ball?
I don't think the physics of what barra said works at all - I'm going to guess that many, perhaps most passes speed up compared to being held by a runner, because the passer supplies power to make the ball move.
To think of it another way - most passes should cover distance much more quickly than if the ball was being carried by a runner, which means they must by definition move faster. So picture, for instance, a quality cut-out pass that covers half the field - simply no way the ball can be carried that quickly, and actually most big passes involve the passer slowing down, so they have more wind-up power and control.
Last article I saw the NRL were working with a type of Hawkeye-like technology that could track the relative ball position on the field. They weren't judging forward passes by straight lines on the field, because as noted, passes from a runner will travel forward relative to the point the ball was release. Rather, the technology they were looking at was basically measuring whether passes left the player's hands in a backwards direction (or not) - which is the law of the pass.
I assume it's fairly complicated to measure the physics and why they need some kind of ball chip and multi-angle system to measure ball movement relative to the camera. Probably also in a fashion similar to how cricket cams predict ball trajectory for LBW referrals.
Annesley did say at the time - if the technology could not get it right near 100% of the time then there was no point introducing it.
The physics works perfectly, if you only think in one dimension, up and down the field. Hypothetically, if the technology only measured the balls speed in one axis it would work in every case and scenario and the ball "floating" forward problem is taken out of it. If the balls velocity increases towards the opposition line, its a forward pass, if it stays the same or slows its legal.
I have never thought of it that way, I always assume it was some sort of ball tracking or "hawk eye" thing, but that system makes a lot of sense and would work in every situation.
But it wouldn't work in every situation as there are other variables in play. If a player is accelerating and passes the ball backwards it is still possible for the ball to go backwards out of the hands and still increase it's forward speed..
That is without going into how a change of direction of a player can increase the balls forward speed.
No it cant. The only way the ball can increase its speed (accelerate) is if a force is acting on it. Once a force is not acting on it, there is no acceleration. its been this way since Newton was a boy.
In your example, imagine JAC sprints from a dead start to near top speed, accelerating very fast and at the point he was going to pass, just let go of the ball. From dead stop the ball accelerates at the same rate as JAC. At the point JAC lets go of the ball, if we forget about air friction and wind etc) the ball would stop accelerating (there is no longer a force acting on it, JACs legs) and the ball would continue on at the same velocity as when JAC let go of the ball (it would obviously slow very slightly due to air and wind and then obviously slow when it hits the ground).
In the same situation, if JAC passes it instead of letting go of it, if the velocity of the ball in the north south axis increases (accelerates) this means and additional force has been applied to the ball in that direction, a literal forward pass. If not, its legal.
Very explained, stupidly I already knew this, that is the problem with multi-tasking lol
In memory of Geoff Chisholm (1965-2022)
F=ma is only true in a straight line. The more precise way of expressing the equation is (see diagram) Where F and a have direction.
The issue is you need to understand vectors and vector arithmetic to get the true direction of the ball. Also what direction is the ball in relation to?That’s why I believe we need a more precise definition of a forward pass.Few things Mike. F=Ma is true in all circumstances, everywhere, in all corners of the universe since the big bang. F=Ma is not only true in a straight line. F, M and a are all vectors and therefore the direction of each is a factor of each together. The direction is part of the vector.
The issue isnt that I need to understand vectors and vector arithmetic, I passed that section (the first week) of my BSc at USyd. The direction of the ball is completely irrelevant, the direction of the F and the a, relative to the north south axis (toward the opponents goal line) is all that matters and that is literally the existing definition of a forward pass.
Not going to argue about F=ma, I know what I meant. What about the z axis?. It’s not as straight forward as people are trying to make out. You need at least a three dimensional coordinate system to determine the direction of the ball.
As you say the current definition is as you stated, but is that good enough? We know that is not it how it is interpreted by the officials.
So what really is a forward pass? Is it not moving towards the opponents goal line (current definition). We know that isn’t right. Is it leaving the persons hands in a backwards direction? That may not be right either because of the position, orientation, direction and rotation of the player. Like I said we need a more precise definition before any tech solution is even considered.
F=ma is only true in a straight line. The more precise way of expressing the equation is (see diagram) Where F and a have direction.
The issue is you need to understand vectors and vector arithmetic to get the true direction of the ball. Also what direction is the ball in relation to?That’s why I believe we need a more precise definition of a forward pass.Few things Mike. F=Ma is true in all circumstances, everywhere, in all corners of the universe since the big bang. F=Ma is not only true in a straight line. F, M and a are all vectors and therefore the direction of each is a factor of each together. The direction is part of the vector.
The issue isnt that I need to understand vectors and vector arithmetic, I passed that section (the first week) of my BSc at USyd. The direction of the ball is completely irrelevant, the direction of the F and the a, relative to the north south axis (toward the opponents goal line) is all that matters and that is literally the existing definition of a forward pass.
Not going to argue about F=ma, I know what I meant. What about the z axis?. It’s not as straight forward as people are trying to make out. You need at least a three dimensional coordinate system to determine the direction of the ball.
No you dont at all. That is the whole point. Everything exists in 3 dimensions, and everything moves in 3D, x, y, z. You might know what you meant but with respect (I mean that, Im not trying to be a know all or argumentative), you are wrong.
When you said F=Ma only works in a straight line and you raised vectors, but again politely, the point you raise suggests to me you dont know what that means and the only reason I raise this is NOT to say "na na ne na na...i know something you dont know", I raise it because it literally directly answers the points you raise and solves the "insolvable" problem you raise.
The way vectors works is not about direction or straight lines. It is about ALL directions at once. I'll try to explain with an example to explain my point as well as show why I think that Barra's example or system works perfectly and actually would solve the problem.
In my example (X north south, Y towards sideline, Z up down) JAC is either running with the ball (1kg) directly straight ahead towards the opposition goal line at constant velocity...or....he is standing dead still. In both circumstances, there is zero acceleration (zero net force excluding gravity). From this point JAC passes a massive forward pass at exactly 45degrees towards the opposition corner post. To do this he applies 10N force at that 45degree angle relative to x, y and 0degrees Z (horizontal, disregarding gravity). The ball accelerates (changes velocity) at 10m per second per second in this 45degree direction. BUT this is the way vectors work. That pass with the force at 45degree has a force component in every direction and the force in the x axis is 5N and therefore the acceleration in the x axis (toward the opposition goal line) is 5m per sec per sec. The component of F on the x axis is positive, on a legal pass it would be negative.
The point being because of the vector nature of force and acceleration, you can determine the component of the force in any direction and because of the forward pass rule, all we care about is the component of the force in the x axis (toward the opponents tryline). The direction of the ball doesnt matter at all. All that matters is the component of force and therefore acceleration in the direction of the oppositions goal line. The rule is that you cant propel (apply force) the ball in the direction of the opposition goal line. Measuring the component of the force vector in the direction of the oppositions goal line is literally measuring against the rule.
As you say the current definition is as you stated, but is that good enough? We know that is not it how it is interpreted by the officials.
The current definition the right rule IMO because it allows for reality (a ball passed back out of the hands, floating forwards) but the officials (all humans) are not able to interpret it exactly and perfectly because they arent equipped. All they can do is make their best estimate and what they think happened. Im not necessarily for using this technology because I dont like the idea of more stoppages due to tech but all Im saying is that the tech proposal that Barra raised would police the rule perfectly and solve all the issues raised here (floating forward, flick passes etc). It would work perfectly in theory.
So what really is a forward pass? Is it not moving towards the opponents goal line (current definition).
The current definition isnt the ball moving towards the opponents goal line. It is that you cant propel the ball towards the opponents goal line i.e. push (force) forward out of the hands towards the opponents goal line and Barras explanation addresses this perfectly.
We know that isn’t right. Is it leaving the persons hands in a backwards direction? That may not be right either because of the position, orientation, direction and rotation of the player. Like I said we need a more precise definition before any tech solution is even considered.
No its literally pushing the ball out of the hands towards the oppositions goal line. Full stop. Thats the rule and it works in all circumstances, regardless of what direction the player is standing, looking or running. What direction is the force from the hands. Barras suggestion addresses this perfectly.
F=ma is only true in a straight line. The more precise way of expressing the equation is (see diagram) Where F and a have direction.
The issue is you need to understand vectors and vector arithmetic to get the true direction of the ball. Also what direction is the ball in relation to?That’s why I believe we need a more precise definition of a forward pass.Few things Mike. F=Ma is true in all circumstances, everywhere, in all corners of the universe since the big bang. F=Ma is not only true in a straight line. F, M and a are all vectors and therefore the direction of each is a factor of each together. The direction is part of the vector.
The issue isnt that I need to understand vectors and vector arithmetic, I passed that section (the first week) of my BSc at USyd. The direction of the ball is completely irrelevant, the direction of the F and the a, relative to the north south axis (toward the opponents goal line) is all that matters and that is literally the existing definition of a forward pass.
Not going to argue about F=ma, I know what I meant. What about the z axis?. It’s not as straight forward as people are trying to make out. You need at least a three dimensional coordinate system to determine the direction of the ball.
No you dont at all. That is the whole point. Everything exists in 3 dimensions, and everything moves in 3D, x, y, z. You might know what you meant but with respect (I mean that, Im not trying to be a know all or argumentative), you are wrong.
When you said F=Ma only works in a straight line and you raised vectors, but again politely, the point you raise suggests to me you dont know what that means and the only reason I raise this is NOT to say "na na ne na na...i know something you dont know", I raise it because it literally directly answers the points you raise and solves the "insolvable" problem you raise.
The way vectors works is not about direction or straight lines. It is about ALL directions at once. I'll try to explain with an example to explain my point as well as show why I think that Barra's example or system works perfectly and actually would solve the problem.
In my example (X north south, Y towards sideline, Z up down) JAC is either running with the ball (1kg) directly straight ahead towards the opposition goal line at constant velocity...or....he is standing dead still. In both circumstances, there is zero acceleration (zero net force excluding gravity). From this point JAC passes a massive forward pass at exactly 45degrees towards the opposition corner post. To do this he applies 10N force at that 45degree angle relative to x, y and 0degrees Z (horizontal, disregarding gravity). The ball accelerates (changes velocity) at 10m per second per second in this 45degree direction. BUT this is the way vectors work. That pass with the force at 45degree has a force component in every direction and the force in the x axis is 5N and therefore the acceleration in the x axis (toward the opposition goal line) is 5m per sec per sec. The component of F on the x axis is positive, on a legal pass it would be negative.
The point being because of the vector nature of force and acceleration, you can determine the component of the force in any direction and because of the forward pass rule, all we care about is the component of the force in the x axis (toward the opponents tryline). The direction of the ball doesnt matter at all. All that matters is the component of force and therefore acceleration in the direction of the oppositions goal line. The rule is that you cant propel (apply force) the ball in the direction of the opposition goal line. Measuring the component of the force vector in the direction of the oppositions goal line is literally measuring against the rule.
As you say the current definition is as you stated, but is that good enough? We know that is not it how it is interpreted by the officials.
The current definition the right rule IMO because it allows for reality (a ball passed back out of the hands, floating forwards) but the officials (all humans) are not able to interpret it exactly and perfectly because they arent equipped. All they can do is make their best estimate and what they think happened. Im not necessarily for using this technology because I dont like the idea of more stoppages due to tech but all Im saying is that the tech proposal that Barra raised would police the rule perfectly and solve all the issues raised here (floating forward, flick passes etc). It would work perfectly in theory.
So what really is a forward pass? Is it not moving towards the opponents goal line (current definition).
The current definition isnt the ball moving towards the opponents goal line. It is that you cant propel the ball towards the opponents goal line i.e. push (force) forward out of the hands towards the opponents goal line and Barras explanation addresses this perfectly.
We know that isn’t right. Is it leaving the persons hands in a backwards direction? That may not be right either because of the position, orientation, direction and rotation of the player. Like I said we need a more precise definition before any tech solution is even considered.
No it’s literally pushing the ball out of the hands towards the oppositions goal line. Full stop. Thats the rule and it works in all circumstances, regardless of what direction the player is standing, looking or running. What direction is the force from the hands. Barras suggestion addresses this perfectly.
Well I disagree on all counts. I just disagree with pretty much your interpretation of all the above. It’s not as straight forward as you and Barra are making out period. The rule needs to be updated if tech is going to be used. I don’t particularly care what the rule is but as it stands now it is not precise enough for tech to be used.
Apologies for killing discussion with dry boring physics.....as you were...is it a good idea?
Whilst the physics discussion is good, ultimately it doesn't help to get bogged down in the technicalities at this time. For example whilst I can understand the argument, as clarified by barra, that any non-forward pass in a forward-back plane (only) should not accelerate towards forward, I am not sure if that would always work if the player is running sideways or backwards, or in the case of a hand-off / offload, or if the ball makes a dramatic motion prior to being released (e.g. a flick pass or being held out in front of the body).
And then it becomes moot anyway because there may not be any device capable of measuring acceleration in a single plane forward-back.
What you really have to do is debate the technology when they tell us exactly what it is doing. I still suspect they are working on some kind of vector measurement device, which tracks ball movement in 3D space and applies some kind of rule for how "backwards" the ball must travel from its release point. Even being able to measure release point may be extremely difficult (whereas in tennis or cricket that isn't a factor at all).
Whilst the physics discussion is good, ultimately it doesn't help to get bogged down in the technicalities at this time. For example whilst I can understand the argument, as clarified by barra, that any non-forward pass in a forward-back plane (only) should not accelerate towards forward, I am not sure if that would always work if the player is running sideways or backwards, or in the case of a hand-off / offload, or if the ball makes a dramatic motion prior to being released (e.g. a flick pass or being held out in front of the body).
And then it becomes moot anyway because there may not be any device capable of measuring acceleration in a single plane forward-back.
What you really have to do is debate the technology when they tell us exactly what it is doing. I still suspect they are working on some kind of vector measurement device, which tracks ball movement in 3D space and applies some kind of rule for how "backwards" the ball must travel from its release point. Even being able to measure release point may be extremely difficult (whereas in tennis or cricket that isn't a factor at all).
I think the reason that I got a little wrapped up in the physics talk, is because (to me) Barras example actually simplified it and I think it would be very easy to do technically. If the ball has a chip then the GPS element measures it motion and it is a relatively simple calculation (simple high school trig) to calculate the component of the vector travelling exactly north south and whether it accelerates in that direction (ie being pushed or passed in a forward motion).
Im not getting caught up in it again. IMO the technicalities of it is easy and IMO it would not be difficult to do that.
A trickier question that to me is not easier to answer with Newtonian physics, is do we WANT them to do that. Even if the tech and physics is 100%, do we want it to go down that path? Increased stoppages? Another reason to pull back a Tigers try etc?
@tiger5150 thanks for the class! You have interpreted exactly what I was thinking - the one and only aspect that is relevant is the change of speed of the ball in the A to B direction once it leaves the hands.
To answer the 'want' question, from a personal point of view I would want it. But only if it is to be accurate (of course), and quickly administered. In my mind, the programme would simply flag the forward movement immediately which would be at least as quick as when a ref currently observes and blows the whistle. I'm not a huge fan of the bunker but that's mainly because humans are still making the decision, (and to a certain extent the time that it takes). The technology I described takes the human error entirely out of the adjudication and is immediately calculated.
That's how it is in my mind anyway!
Whilst the physics discussion is good, ultimately it doesn't help to get bogged down in the technicalities at this time. For example whilst I can understand the argument, as clarified by barra, that any non-forward pass in a forward-back plane (only) should not accelerate towards forward, I am not sure if that would always work if the player is running sideways or backwards, or in the case of a hand-off / offload, or if the ball makes a dramatic motion prior to being released (e.g. a flick pass or being held out in front of the body).
And then it becomes moot anyway because there may not be any device capable of measuring acceleration in a single plane forward-back.
What you really have to do is debate the technology when they tell us exactly what it is doing. I still suspect they are working on some kind of vector measurement device, which tracks ball movement in 3D space and applies some kind of rule for how "backwards" the ball must travel from its release point. Even being able to measure release point may be extremely difficult (whereas in tennis or cricket that isn't a factor at all).
I think the reason that I got a little wrapped up in the physics talk, is because (to me) Barras example actually simplified it and I think it would be very easy to do technically. If the ball has a chip then the GPS element measures it motion and it is a relatively simple calculation (simple high school trig) to calculate the component of the vector travelling exactly north south and whether it accelerates in that direction (ie being pushed or passed in a forward motion).
Im not getting caught up in it again. IMO the technicalities of it is easy and IMO it would not be difficult to do that.
A trickier question that to me is not easier to answer with Newtonian physics, is do we WANT them to do that. Even if the tech and physics is 100%, do we want it to go down that path? Increased stoppages? Another reason to pull back a Tigers try etc?
Yes we want it. It should be like the ball-line technology in soccer or net calls in tennis - the ref gets a ping on his watch and makes the call. If the pass isn't forward, the play doesn't even stop.
Whilst the physics discussion is good, ultimately it doesn't help to get bogged down in the technicalities at this time. For example whilst I can understand the argument, as clarified by barra, that any non-forward pass in a forward-back plane (only) should not accelerate towards forward, I am not sure if that would always work if the player is running sideways or backwards, or in the case of a hand-off / offload, or if the ball makes a dramatic motion prior to being released (e.g. a flick pass or being held out in front of the body).
And then it becomes moot anyway because there may not be any device capable of measuring acceleration in a single plane forward-back.
What you really have to do is debate the technology when they tell us exactly what it is doing. I still suspect they are working on some kind of vector measurement device, which tracks ball movement in 3D space and applies some kind of rule for how "backwards" the ball must travel from its release point. Even being able to measure release point may be extremely difficult (whereas in tennis or cricket that isn't a factor at all).
I think the reason that I got a little wrapped up in the physics talk, is because (to me) Barras example actually simplified it and I think it would be very easy to do technically. If the ball has a chip then the GPS element measures it motion and it is a relatively simple calculation (simple high school trig) to calculate the component of the vector travelling exactly north south and whether it accelerates in that direction (ie being pushed or passed in a forward motion).
Im not getting caught up in it again. IMO the technicalities of it is easy and IMO it would not be difficult to do that.
A trickier question that to me is not easier to answer with Newtonian physics, is do we WANT them to do that. Even if the tech and physics is 100%, do we want it to go down that path? Increased stoppages? Another reason to pull back a Tigers try etc?
Yes we want it. It should be like the ball-line technology in soccer or net calls in tennis - the ref gets a ping on his watch and makes the call. If the pass isn't forward, the play doesn't even stop.
Except it’s not like either. They are destination technologies. ie what happens to the ball at its destination. Tech about forward passes would be source technology ie. what happens at the beginning of its travels.
I have a very simple question in the regards to the source. How would the tech determine when the ball had left the players hands?
