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Post by volleydadtx on Jul 10, 2021 23:54:47 GMT -5
This may be the source of the problem here. I find it implausible that the ball will accelerate between the point of contact and the time it reaches the net. I'm by no means an expert on this but, that was my first reaction as well. But on further thought, without knowing the terminal velocity of a volleyball or the drag coefficient, it would be hard to say without testing. yes I agree. What I meant to say is that the volleyball has reached its maximum speed on the other side of the net as it crosses the net. The contact point would be the highest velocity, but that can't be measured properly with a radar gun. |
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Post by silverchloride on Jul 11, 2021 0:07:06 GMT -5
True dat, but even the shortest player on the team can easily jump above the 7 foot 4 1/4 inch women's net. So, using the info previously given for my kid, hypothetically, she is making contact at about 110 inches, That is about 22 inches above the net. A statistically significant difference from the 79 inch height in your experiment. I could still be wrong =) I can pretty much guarantee your kiddo isn't making contact on a serve @ 110 inches unless she's in training at Colorado Springs. I set the contact point at 7.5 feet. That's 90 inches. Ah, 7 feet 6 inches. I made a typographical error, I meant 7 feet 9 inches, or 89 inches. A 21 inch vert on the serve does not seem that unusual at the elite level. Her touch would be 114 inches, I just subtracted 4 inches down to the palm. Assuming she makes contact at the apex of her arc, but that does not always happen. |
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Post by justahick on Jul 11, 2021 0:54:40 GMT -5
I can pretty much guarantee your kiddo isn't making contact on a serve @ 110 inches unless she's in training at Colorado Springs. I set the contact point at 7.5 feet. That's 90 inches. Ah, 7 feet 6 inches. I made a typographical error, I meant 7 feet 9 inches, or 89 inches. A 21 inch vert on the serve does not seem that unusual at the elite level. Her touch would be 114 inches, I just subtracted 4 inches down to the palm. Assuming she makes contact at the apex of her arc, but that does not always happen. A couple of things to consider... Most jump floats typically aren't anywhere near max vertical, probably closer to 50% of max Float serves are usually with arms not fully extended. A 6' player with average reach would touch about 8' standing. Arm bent brings her fingertips down to closer to 7' 3", and the bottom of the palm closer to 6' 9". Add 12" for a semi-jump get bottom of the ball to 7' 9". |
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Post by sevb on Jul 11, 2021 1:13:18 GMT -5
Here's a fun twist...
How long does it take for a ball to get from point of serve to the endline at a given velocity?
Now take that amount of time and subtract the time it takes an athlete to recognize and act on the serve as it moves from point A towards point B...
NOW how much time is left for the Passer in question to actually perform the skill necessary to redirect the ball towards the net... Or into the 3rd row...
And given THAT amount of time readjust the distance from the serving machine and just play dodge ball ... Theres less math invlved
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Post by Maui’s Hook on Jul 11, 2021 13:56:23 GMT -5
Here's a fun twist... How long does it take for a ball to get from point of serve to the endline at a given velocity? Now take that amount of time and subtract the time it takes an athlete to recognize and act on the serve as it moves from point A towards point B... NOW how much time is left for the Passer in question to actually perform the skill necessary to redirect the ball towards the net... Or into the 3rd row... And given THAT amount of time readjust the distance from the serving machine and just play dodge ball ... Theres less math invlved 40mph into feet per second is 58.67. Pretty convenient speed given court dimensions. |
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Post by oldnewbie on Jul 11, 2021 16:22:13 GMT -5
Here's a fun twist... How long does it take for a ball to get from point of serve to the endline at a given velocity? Now take that amount of time and subtract the time it takes an athlete to recognize and act on the serve as it moves from point A towards point B... NOW how much time is left for the Passer in question to actually perform the skill necessary to redirect the ball towards the net... Or into the 3rd row... And given THAT amount of time readjust the distance from the serving machine and just play dodge ball ... Theres less math invlved 40mph into feet per second is 58.67. Pretty convenient speed given court dimensions. Yup. This has been misstated a couple of times, which may be a big part of the confusion. In addition, 45 mph into feet per second is 66 ft/s. Also pretty convenient, since a 9m court corner to corner is 20.12m or 66 feet. volleydadtx mentioned 1/4 second after it crosses the net, which may be the faulty assumption causing the confusion. It should be 1/2 second after it crosses the net. That makes a huge difference. Assuming no deceleration, you can serve corner to corner at a constant 45mph in 1 second. The drop due to gravity for 1 second is 14.78 feet, but only 3.6 feet of that drop is in the first 1/2 second. That means the ball would drop 11.18 feet due to gravity at those speeds and distances AFTER the ball crosses the net. That should give plenty of room to land even a 45mph float serve, even before you start to account for deceleration. |
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Post by sevb on Jul 11, 2021 16:27:37 GMT -5
and… it must be noted… the ball doesn’t necessarily have to be “in”… it just has to be close enough for the SR passers to “think” that it’s in…
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Post by crando on Jul 11, 2021 16:48:25 GMT -5
Lots of people saying smart things on here -- I like it! I had a HS sophomore who was hitting jump-floats at 39-40 mph and putting them in the court (based on my PocketRadar and dozens and dozens of samples). She was a quite good player, but ended up being not Power-5 level -- so basically 1 in 100 instead of 1 in a million. From conversations I've had with other coaches, and a couple posts in this thread, I don't think that was super-rare. Quite good, but semi-common. She was probably touching 9-6 to 9-8 (on her best max jump, and fingertip reach, of 5 trials...). Since you don't max-jump on a serve and you don't max-extend your arm to hit a float, let's say she was touching 8-8 to 8-10 on the serve, so the bottom of the ball was just over 8 feet. Thus she probably had to hit the ball slightly up, since gravity would make it dip more than 7 1/2 inches (??) before it reaches the net. For whatever all that is worth... To the original poster I'd say this: the ball is going to have a good amount of drag; by the time an untouched serve hits the floor, its horizontal speed has slowed a lot. So I believe that a ball leaving the hand at 40 mph is doable, but a ball going 40 mph when it crosses the net is always going to be out (and it left the hand/serving machine probably around 45-46??). So I think we're all saying the same thing, in different ways. The PocketRadar said line up right in front, or behind, the server and push the button just before contact -- so it's probably reading pretty close to the contact moment (before the ball has slowed at all). Not sure what you were doing to get the reading at the net-crossing, but if you were, then my 40-mph serve (and silverchloride's, and joetrinsey's, and probably the initial passer) is definitely a slower serve than your 40-mph serve. And for a ball with no spin, how fast it can go and still be in is based on 4 things (assuming it crosses JUST above the net; crossing higher means you can't hit it as fast): 1) What is the horizontal speed when crossing the net (how much time will it take to get from the net to the endline -- i.e. how much time does gravity have to "pull" the ball down from 7' 4" to the ground)? 2) What is the angle of the serve to the perpendicular (serving crosscourt means the endline is actually more than 30' from the net, so gravity has more time to work)? 3) What is the downward angle when it crosses the net (if you serve from 11 feet and hit the ball downward, obviously you can hit it a lot harder)? We're assuming that pretty close to flat is reasonable for most servers -- if I contact it at 7'9" then it probably goes slightly up at the beginning, but has probably had its path bent by gravity to be going slightly downward when it crosses the net, then continues to bend downward from there. 4) How much is the air-drag (higher barometric pressure, and/or more humid air, probably leads to more drag, so you can hit the ball harder -- the ball will slow even more from net to endline, so gravity can help more; conversely, at altitude, with less air, the ball slows down less as it flies through the air)? Gravity is 32 ft/sec/sec? So if a ball falls for 0.7 seconds, with no air resistance, its downward velocity will accelerate from 0 feet/sec to 22.4 feet/sec, so an average speed of 11.2 feet/sec during that 0.7 seconds, so it will fall 7.84 feet (5 inches above a women's net). So if the ball crosses the net horizontally (a big if...), if it goes from the net to the endline (on a line serve, perpendicular to the net) in less than about 0.7 seconds, it will be out. So if the ball's average speed from net to endline is higher than (30 feet/.7 sec, or 43 feet/sec, or...) about 29.3 mph, it won't be able to fall from the net height to the ground before it reaches the endline... That said, if the ball averaged 30 mph from my hand to the net, it would fall 7+ feet then too, so (unless I contact the serve at like 14 feet) I need to aim at a spot WAY above the net. But when I do that, the ball is already coming down at an angle when it crosses the net, so it can be moving faster than 29.3? And I don't aim that high, because the ball's average speed from my hand to the net is way faster than the average speed from the net to the endline, because drag is reducing the ball's speed way more than we might appreciate? So the ball falls a lot less from hand-to-net, than from net-to-endline, because its speed is continuously decreasing due to air drag. But I have no idea how much... That's all I got -- we need someone with a wind tunnel  |
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Post by oldnewbie on Jul 11, 2021 18:18:46 GMT -5
Gravity is 32 ft/sec/sec? So if a ball falls for 0.7 seconds, with no air resistance, its downward velocity will accelerate from 0 feet/sec to 22.4 feet/sec, so an average speed of 11.2 feet/sec during that 0.7 seconds, so it will fall 7.84 feet (5 inches above a women's net). So if the ball crosses the net horizontally (a big if...), if it goes from the net to the endline (on a line serve, perpendicular to the net) in less than about 0.7 seconds, it will be out. So if the ball's average speed from net to endline is higher than (30 feet/.7 sec, or 43 feet/sec, or...) about 29.3 mph, it won't be able to fall from the net height to the ground before it reaches the endline... That said, if the ball averaged 30 mph from my hand to the net, it would fall 7+ feet then too, so (unless I contact the serve at like 14 feet) I need to aim at a spot WAY above the net. Where does 0.7 seconds come from? We are talking about an end line to end line distance from 59 feet (shortest distance) to 66 feet (cross court max). Disregarding any horizontal deceleration (to keep it simple), 0.7 seconds would give a speed range of between 57.5 mph and 64.29 mph. That is much faster than the serving speeds we are talking about here. |
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Post by jammaster on Jul 11, 2021 18:54:55 GMT -5
The ball generally has reached its fastest point as it crosses the net. This may be the source of the problem here. I find it implausible that the ball will accelerate between the point of contact and the time it reaches the net. Agree...no acceleration without force being placed on the ball. Just drag of a ball moving through air...clearly the ball slows from moment of completion of contact. |
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Post by sonofdogman on Jul 11, 2021 19:27:54 GMT -5
I did this experiment once, but made the mistake of measuring in feet per meter.
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Post by dodger on Jul 11, 2021 20:41:27 GMT -5
This may be the source of the problem here. I find it implausible that the ball will accelerate between the point of contact and the time it reaches the net. Good point. There might be a very slight difference, but there's no real way to measure the speed of the serve at the point of contact. What I was meaning to say is that the ball is at its fastest point on the other side of the net as it crosses the net. The serve speed is useful only as it relates to the serve having to be passed, which is the other side of the net. Also, gravity is also supplementing the speed as the ball descends. It's probably a net wash. Just the facts: the reason i asked for the gun height is because if high enough it is reading the ball in the first few feet it travels: the speed at contact is the fastest the ball will be going: for every 7 feet the ball travels it slows down by approximately (at least) 1 mph: rounding up you are serving ball at least 50 feet so ball has slowed down at least 7 mph and could be more depending on a few variables: therefore the brand of speed gun, location on court (height closeness to ball machine), will have a cariablity of mph readings: and if a study you read uses video, and they use mph as ball speed need to read carefuly: because it they use time and distance (distance being from contact to pass) this would be and average speed because the ball is constantly decelerating from contact to pass: if you want a passer to practice just time how long from serve till passer contact: anytime from .9 sec. to 1.2 sec. will stress out your setve receiver! ps: your serving machine needs to be at at least 8 feet for a good average of possible release points! |
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Post by dodger on Jul 11, 2021 20:43:14 GMT -5
I can pretty much guarantee your kiddo isn't making contact on a serve @ 110 inches unless she's in training at Colorado Springs. I set the contact point at 7.5 feet. That's 90 inches. Ah, 7 feet 6 inches. I made a typographical error, I meant 7 feet 9 inches, or 89 inches. A 21 inch vert on the serve does not seem that unusual at the elite level. Her touch would be 114 inches, I just subtracted 4 inches down to the palm. Assuming she makes contact at the apex of her arc, but that does not always happen. Jump float servers rarely jump very high when executing jump serve! Using max jump and standing reach to approximate would be a very poor way of attempting this predicted contact poitn |
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Post by silverchloride on Jul 11, 2021 21:16:51 GMT -5
Ah, 7 feet 6 inches. I made a typographical error, I meant 7 feet 9 inches, or 89 inches. A 21 inch vert on the serve does not seem that unusual at the elite level. Her touch would be 114 inches, I just subtracted 4 inches down to the palm. Assuming she makes contact at the apex of her arc, but that does not always happen. Jump float servers rarely jump very high when executing jump serve! Using max jump and standing reach to approximate would be a very poor way of attempting this predicted contact poitn Twenty one is not her max, but 14-18 inches is probably a more accurate jump float serve jump. Still puts her contact above the net height. In either case, I am certain about her target speeds and it seems to work most of the time =) |
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Post by dodger on Jul 11, 2021 21:33:44 GMT -5
Calculating projectile isn't just horizontal an vertical velocity’s (mph’ or ft/sec) example: a ball having initial velocity of 40 mph (58.667ft/s), at an initial upward trajectory of 2 degree’s , contacted at 9’ above court, will reach a max height of 9.06 feet, travel 46.30 feet, it will take .81secs to get there,
So if i hit jump float at 40 mph contacting ball 9’ above court, it will travel 46.3 feet before hitting floor reaching a max height of 9.06 feet.
This is the calculation for a projectile starting at a height above floor , receiving an initial horizontal velocity, and the upward angle of the projectile. From that you calculate m, time in air, distance traveled, max height achieved.
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