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Post by sevb on Jul 10, 2021 23:00:18 GMT -5
I'd love to hear any of the scientists that frequent the board respond... There are several... But unless the machine (most use spinning wheels to accelerate the ball) can mimic the impact of the hand on a ball (small impact point that dents the bladder)... Then the two different methods can't be compared accurately... It's apple pie to peach cobbler...
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Post by mikegarrison on Jul 10, 2021 23:18:54 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. |
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Post by volleydadtx on Jul 10, 2021 23:32:24 GMT -5
Just as a caveat, men serve much faster, and still get in the court, so it must be possible =) Player Speed 1. Wilfredo Leon 134 km/h (83.26 mph) 2. Ivan Zaytsev 134 km/h (83.26 mph) 3. Matey Kaziyski 132.9 km/h (82.58 mph) 4. Ivan Zaytsev 130.9 km/h (81.34 mph) 1. Those are not float serves. They are power jump serves with massive top spin. 2. Comparing men and women isn't worthwhile. Men have the physique and vertical to hit a volleyball sharply down at contact and it still clear the net with ease. |
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Post by volleydadtx on Jul 10, 2021 23:35:23 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. 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. |
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Post by volleydadtx on Jul 10, 2021 23:37:27 GMT -5
I'd love to hear any of the scientists that frequent the board respond... There are several... But unless the machine (most use spinning wheels to accelerate the ball) can mimic the impact of the hand on a ball (small impact point that dents the bladder)... Then the two different methods can't be compared accurately... It's apple pie to peach cobbler... Disagree. A ball with no spin is a ball with no spin, regardless of the source. |
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Post by volleydadtx on Jul 10, 2021 23:39:29 GMT -5
The question is: what kind of radar gun used: location of radar gun: etc etc: a study done of woman's jump float serve serve done in a pro league tourney in Spain: 151 players served: 2056 serves evaluated, and measured with calculations when balls angle isn't directly at speed gun. The range of speed for these jump float servers was 24.8mph to 38.5mph. It would seem that the player your referring: isn't serving at the velocity’s your quoting unless its due to the way its being measured and vice versa: I do not know, what I do not know =) But, seen it with my own eyes, perhaps I just do not know what I am looking at. would love to see a link of your daughter's highlights. Sounds like she's a beast for sure. |
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Post by mikegarrison on Jul 10, 2021 23:40:50 GMT -5
So the net height is 2.24 meters. Call it 2.5 meters for the ball to just clear the net. If the point of contact is 3.25 meters, the ball has dropped only .75 meters in total as it crosses the net. (For this purpose it doesn't matter that it arced up and then back down.) That's a gain of 0.75 meters * 9.8 meters/sec^2 * 0.27 kg of energy from lost potential energy.
If we assume it's moving at about 16 meters/second, we can figure out that its kinetic energy is 34.5 Joules. The potential energy it lost is only 2 Joules. So at most (ignoring any drag), it can pick up about 0.44 m/s from the fact that it is now lower than at the point of contact.
I am very comfortable estimating that it is losing energy to drag faster than it may be picking it up from dropping in height.
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Post by volleydadtx on Jul 10, 2021 23:42:28 GMT -5
So the net height is 2.24 meters. Call it 2.5 meters for the ball to just clear the net. If the point of contact is 3.25 meters, the ball has dropped only .75 meters in total as it crosses the net. (For this purpose it doesn't matter that it arced up and then back down.) That's a gain of 0.75 meters * 9.8 meters/sec^2 * 0.27 kg of energy from lost potential energy. If we assume it's moving at about 16 meters/second, we can figure out that its kinetic energy is 34.5 Joules. The potential energy it lost is only 2 Joules. So at most (ignoring any drag), it can pick up about 0.44 m/s from the fact that it is now lower than at the point of contact. I am very comfortable estimating that it is losing energy to drag faster than it may be picking it up from dropping in height. ok you just went above my pay grade, Mike, so I'm going with you on this one.  |
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Post by justahick on Jul 10, 2021 23:43:20 GMT -5
Here's a study done with some elite level women which seems to be in the same ball park www.frontiersin.org/articles/10.3389/fspor.2020.559277/fullAverage velocity at contact for jump float was 17.19 m/s = 39.77 mph or, doing the math (ignoring drag, just to get a rough idea) a ball at height 7.5 feet at the net will drop in .685 seconds to land in it can travel 29.5 ft max velocity at net 29 mph (actually closer to 35 ft if serving corner to corner) max velocity at net 34 mph Accounting for drag, a max release velocity near 40 mph isn't unreasonable. Both empirical and calculated maximums appear to confirm the serving machine testing from the OP. |
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Post by silverchloride on Jul 10, 2021 23:44:16 GMT -5
Just as a caveat, men serve much faster, and still get in the court, so it must be possible =) Player Speed 1. Wilfredo Leon 134 km/h (83.26 mph) 2. Ivan Zaytsev 134 km/h (83.26 mph) 3. Matey Kaziyski 132.9 km/h (82.58 mph) 4. Ivan Zaytsev 130.9 km/h (81.34 mph) 1. Those are not float serves. They are power jump serves with massive top spin. 2. Comparing men and women isn't worthwhile. Men have the physique and vertical to hit a volleyball sharply down at contact and it still clear the net with ease. 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 =) |
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Post by silverchloride on Jul 10, 2021 23:47:00 GMT -5
I do not know, what I do not know =) But, seen it with my own eyes, perhaps I just do not know what I am looking at. would love to see a link of your daughter's highlights. Sounds like she's a beast for sure. I appreciate that, but I do not use this forum to promote my daughter. Anonymity and all =) |
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Post by justahick on Jul 10, 2021 23:47:29 GMT -5
I'd love to hear any of the scientists that frequent the board respond... There are several... But unless the machine (most use spinning wheels to accelerate the ball) can mimic the impact of the hand on a ball (small impact point that dents the bladder)... Then the two different methods can't be compared accurately... It's apple pie to peach cobbler... Disagree. A ball with no spin is a ball with no spin, regardless of the source. I'm not so sure. The deformation of the ball will be different and MAY impact the behavior of the ball. BTW - Not at all sure it makes any practical difference. I expect the float of the ball will be similar enough as to be indistinguishable by human eyes. |
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Post by volleydadtx on Jul 10, 2021 23:47:58 GMT -5
Here's a study done with some elite level women which seems to be in the same ball park www.frontiersin.org/articles/10.3389/fspor.2020.559277/fullAverage velocity at contact for jump float was 17.19 m/s = 39.77 mph or, doing the math (ignoring drag, just to get a rough idea) a ball at height 7.5 feet at the net will drop in .685 seconds to land in it can travel 29.5 ft max velocity at net 29 mph (actually closer to 35 ft if serving corner to corner) max velocity at net 34 mph Accounting for drag, a max release velocity near 40 mph isn't unreasonable. Both empirical and calculated maximums appear to confirm the serving machine testing from the OP. OK now that is some good stuff right there. Thank you for sharing. |
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Post by volleydadtx on Jul 10, 2021 23:50:03 GMT -5
1. Those are not float serves. They are power jump serves with massive top spin. 2. Comparing men and women isn't worthwhile. Men have the physique and vertical to hit a volleyball sharply down at contact and it still clear the net with ease. 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. |
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Post by vergyltantor on Jul 10, 2021 23:51:12 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. 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. |
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