The Trigonometry of Foot Faulting

Z-Man · 08-04-2008, 07:47 PM

Just like everyone else here, I have a regular opponent who foot faults. Just before he makes contact, his left foot lands about 2.5 feet inside the baseline. It drives me nuts.

After playing tonight I started to wonder. Just how much of an advantage is he getting? So I dusted off my high school trig and tried to calculate two things: 1) A 1ft footfault is like being how many inches taller? 1) A 1 ft footfault is like the net being how many inches lower?

It's been 15 years since high school, so I'm hoping you guys can check my math. Here's what I came up with:

1ft = 1.71in taller
2ft = 3.43in taller
2.5ft = 4.28in taller

1ft = net .6in lower
2ft = net 1.24in lower
2.5ft = net 1.56in lower

For the first calculation, I figured the angle from the top of the net to the service line. Using that angle, I figured the height of the contact point at the baseline that would allow you to hit the ball straight across the top of the net to the service line (not taking into account the width of the ball). Then I shortened the distance to the net, and using the same angle, calculated the height needed to hit straight across the top of the net to the service line.

For the second calculation, I kept the contact point height constant and calculated the angle to the service line, which increases as you foot fault. Then I used those angles to calculate the extra inches of net clearance you get as the ball travels across the net to the service line.

Hopefully those of you who are smarter than I am can check my math. If my calculations are correct, footfaulting seem to be a real advantage. I would love to be 4 inches taller without sacrificing mobility, and my flat serve would be smoking if the net was an inch and a half lower...

CHEATERS!!!!!!!!!!!!!!!!!!!!!!

YULitle · 08-04-2008, 07:51 PM

You're gaining more than just physical height or a lower net. You are striking the ball farther forward than you typically would, all else equal, this reducing reaction time.

Z-Man · 08-04-2008, 08:02 PM

Quote:

Originally Posted by YULitle

You're gaining more than just physical height or a lower net. You are striking the ball farther forward than you typically would, all else equal, this reducing reaction time.

Yes indeed! And you also hit that first volley closer to the net, giving you an unfair advantage on your second shot as well. It's a double cheat!

YULitle · 08-04-2008, 08:09 PM

Quote:

Originally Posted by Z-Man

Yes indeed! And you also hit that first volley closer to the net, giving you an unfair advantage on your second shot as well. It's a double cheat!

Triple, even!

Steady Eddy · 08-04-2008, 08:17 PM

Consider the triangle formed by the net, (in a vertical sense), the court, (from net to service line), and the hypotenuse connecting the net to the service line. the rise is 3 ft, and the run is 21 ft, that ratio reduces to 1/7. So every foot of cheating make you 1/7 of a foot taller. I think that's the easiest way to think of it. No need for trig functions, (although you can do it that way). Just geometry.

Z-Man · 08-05-2008, 04:56 AM

Quote:

Originally Posted by Steady Eddy

Consider the triangle formed by the net, (in a vertical sense), the court, (from net to service line), and the hypotenuse connecting the net to the service line. the rise is 3 ft, and the run is 21 ft, that ratio reduces to 1/7. So every foot of cheating make you 1/7 of a foot taller. I think that's the easiest way to think of it. No need for trig functions, (although you can do it that way). Just geometry.

That's a much easier way to figure it...

chess9 · 08-05-2008, 06:23 AM

Cute thread.

The line from the serve to the LZ (landing zone of ball) is not a straight one, btw.

Hypotenuses like straight lines. But, the important issue is not the height advantage, but that the LZ error rate declines at a given velocity.

But, having said all of this, foot faulting is illegal. Those who do it should suffer much more severe consequences than they do. In pro matches they are rarely called (in all fairness, the pros might barely touch the line and any advantage is very minimal), and in local amateur matches calling a footfault would be tantamount to declaring nuclear war. I've seen old men fighting over the issue. Not nice.

-Robert

Steady Eddy · 08-05-2008, 06:17 PM

Quote:

Originally Posted by YULitle

You're gaining more than just physical height or a lower net. You are striking the ball farther forward than you typically would, all else equal, this reducing reaction time.

YU, so are his calculations correct?

YULitle · 08-05-2008, 07:51 PM

Quote:

Originally Posted by Steady Eddy

YU, so are his calculations correct?

I didn't bother to check them. Seems inconsequential, to me.

RakettoKozou · 08-05-2008, 09:17 PM

Quote:

Originally Posted by Z-Man

Yes indeed! And you also hit that first volley closer to the net, giving you an unfair advantage on your second shot as well. It's a double cheat!

Those hackers... they somehow hacked life to double cheat!

TURN OFF YOURR HACKKKSSSS

YULitle · 08-05-2008, 09:22 PM

Quote:

Originally Posted by RakettoKozou

Those hackers... they somehow hacked life to double cheat!

TURN OFF YOURR HACKKKSSSS

Yeah, there needs to be a Punkbuster for tennis!

RakettoKozou · 08-05-2008, 09:24 PM

I think that's called a line judge/umpire. xD

They bust those punks good.

consistency wins · 08-05-2008, 10:56 PM

Screw the trig. Just forewarn them they are faulting and then start calling it.

See...math is simple! Even trig!

chess9 · 08-06-2008, 03:33 AM

Quote:

Originally Posted by RakettoKozou

Those hackers... they somehow hacked life to double cheat!

TURN OFF YOURR HACKKKSSSS

LOL! Good point.

-Robert

Kaptain Karl · 08-06-2008, 08:13 AM

Quote:

Originally Posted by Z-Man

Just like everyone else here, I have a regular opponent who foot faults. Just before he makes contact, his left foot lands about 2.5 feet inside the baseline.

a) That's a HUGE FF!

b)Do you know he steps in that far from watching him play others? Or do you just "think so" from almost 80 feet away?

- KK

Fedace · 08-06-2008, 08:15 AM

FootFaulting is Legal in amateur tennis. and those who call it will be kicked out of the league.

Noaler · 08-06-2008, 08:33 AM

Quote:

Originally Posted by Fedace

FootFaulting is Legal in amateur tennis. and those who call it will be kicked out of the league.

WhAT?!!??!? Define amateur tennis?

Fedace · 08-06-2008, 08:54 AM

Quote:

Originally Posted by Noaler

WhAT?!!??!? Define amateur tennis?

Those USTA leagues that can never get the ratings right and has captains that will do anything to get to the nationals, even give their first born.....

chess9 · 08-06-2008, 08:57 AM

Quote:

Originally Posted by Fedace

FootFaulting is Legal in amateur tennis. and those who call it will be kicked out of the league.

Spot on!

-Robert

Fedace · 08-06-2008, 09:02 AM

Quote:

Originally Posted by chess9

Spot on!

-Robert

I must say, i respect your wisdom on this controversial matter.

08-04-2008, 07:47 PM	#1
Z-Man Professional Join Date: Jan 2005 Posts: 945	The Trigonometry of Foot Faulting Just like everyone else here, I have a regular opponent who foot faults. Just before he makes contact, his left foot lands about 2.5 feet inside the baseline. It drives me nuts. After playing tonight I started to wonder. Just how much of an advantage is he getting? So I dusted off my high school trig and tried to calculate two things: 1) A 1ft footfault is like being how many inches taller? 1) A 1 ft footfault is like the net being how many inches lower? It's been 15 years since high school, so I'm hoping you guys can check my math. Here's what I came up with: 1ft = 1.71in taller 2ft = 3.43in taller 2.5ft = 4.28in taller 1ft = net .6in lower 2ft = net 1.24in lower 2.5ft = net 1.56in lower For the first calculation, I figured the angle from the top of the net to the service line. Using that angle, I figured the height of the contact point at the baseline that would allow you to hit the ball straight across the top of the net to the service line (not taking into account the width of the ball). Then I shortened the distance to the net, and using the same angle, calculated the height needed to hit straight across the top of the net to the service line. For the second calculation, I kept the contact point height constant and calculated the angle to the service line, which increases as you foot fault. Then I used those angles to calculate the extra inches of net clearance you get as the ball travels across the net to the service line. Hopefully those of you who are smarter than I am can check my math. If my calculations are correct, footfaulting seem to be a real advantage. I would love to be 4 inches taller without sacrificing mobility, and my flat serve would be smoking if the net was an inch and a half lower... CHEATERS!!!!!!!!!!!!!!!!!!!!!! Last edited by Z-Man : 08-04-2008 at 07:50 PM.

08-04-2008, 07:51 PM	#2
YULitle Hall Of Fame Join Date: May 2005 Location: Guymon, OK Posts: 4,132	You're gaining more than just physical height or a lower net. You are striking the ball farther forward than you typically would, all else equal, this reducing reaction time. __________________ Michael A. -- If your flaw in stringing is consistency, http://www.youtube.com/yulitle MRT 07-08 -- your stringing will be consistently flawed.

08-04-2008, 08:17 PM	#5
Steady Eddy Hall Of Fame Join Date: Jul 2007 Location: Arizona Posts: 2,127	Consider the triangle formed by the net, (in a vertical sense), the court, (from net to service line), and the hypotenuse connecting the net to the service line. the rise is 3 ft, and the run is 21 ft, that ratio reduces to 1/7. So every foot of cheating make you 1/7 of a foot taller. I think that's the easiest way to think of it. No need for trig functions, (although you can do it that way). Just geometry. __________________ I strive not to laugh at human actions, not to weep at them or to hate them, but to understand them. - Spinoza

08-05-2008, 06:23 AM	#7
chess9 Hall Of Fame Join Date: Dec 2005 Location: 1.d4 Posts: 4,275	Cute thread. The line from the serve to the LZ (landing zone of ball) is not a straight one, btw. Hypotenuses like straight lines. But, the important issue is not the height advantage, but that the LZ error rate declines at a given velocity. But, having said all of this, foot faulting is illegal. Those who do it should suffer much more severe consequences than they do. In pro matches they are rarely called (in all fairness, the pros might barely touch the line and any advantage is very minimal), and in local amateur matches calling a footfault would be tantamount to declaring nuclear war. I've seen old men fighting over the issue. Not nice. -Robert __________________ "Love is the irresistible desire to be irresistibly desired."-Frost Last edited by chess9 : 08-05-2008 at 06:27 AM.

08-05-2008, 09:24 PM	#12
RakettoKozou Rookie Join Date: Jul 2008 Location: SoCal Posts: 258	I think that's called a line judge/umpire. xD They bust those punks good. __________________ http://s13.photobucket.com/albums/a275/z7dude7z/?action=view&current=RakettoKozou.jpg Hmm... Nothing else to put here.