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Post by beachvolleymike on Apr 22, 2012 19:54:29 GMT -5
Why step 10 or 15 feet back to serve a float serve? Does the increased distance let the ball "dance" more in transit?
If anyone can explain the physics behind it, that's the meat of the question I think.
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Post by d3coach on Apr 22, 2012 20:16:14 GMT -5
I am not sure if it is physics so much as the timing of the serve/pass changes. The ball is in the air a lot longer, potentially traveling at a faster velocity, giving the passer a different look.
If there was a physics based effect, since it is in the air longer, gravity should have an exponentially different effect on it, causing it to drop differently than anticipated if the passer isn't used to it.
Personally, I think this serve is only more effective because it is not common, and given club volleyball's setup, players rarely see it in a game setting at a high level until they get to college (maybe).
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Post by vbnerd on Apr 22, 2012 20:37:33 GMT -5
If you step back you can hit it harder, apply more force. The more force on the ball, the greater the impact of the air flow through the seems... I think.
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Post by Deleted on Apr 22, 2012 20:39:08 GMT -5
Aerodynamics, fluid motion, and physics... Sounds like a question for mikegarrison.
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Post by Phaedrus on Apr 22, 2012 20:40:50 GMT -5
Depending on how you contact the ball while serving, there will be spins imparted on the ball. Top spins bring the ball down because the seams are rolling forward, causing the air velocity on top of the ball to be faster than the air velocity below the ball, pushing the ball down. The opposite is true of the back spin, although you would be really hard pressed to "lift" the back spin serve because gravity is working against the action of the back spin, so unless you put a hellacious amount of back spin on the ball it won't really "lift" all that much.
The floater is the no-spin option. People will often compare it to the knuckle ball in baseball. Theoretically, the reason for starting back so far is to ensure that the ball is cutting through as much air as possible, i.e. the longer the ball is in the air the more likely it is to be exposed to the air stream and the more the ball trajectory will change. My personal opinion is that the longer time in the air will psychologically affect the passer more than the aerodynamic effect. the passer has to pay attention to the floater and try to track its path, the longer the passer has to look at how the ball is moving, the more the passer is moving themselves to adjust to the movement, thereby increasing their chances of making mistakes or making an aggressive but erroneous move to the ball which might be difficult to recover from.
The jump serve part serves to change the contact point of the serve so that the ball is seemingly coming down towards the passer and forces the passer to react to a different trajectory.
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Post by mikegarrison on Apr 22, 2012 21:28:16 GMT -5
Depending on how you contact the ball while serving, there will be spins imparted on the ball. Top spins bring the ball down because the seams are rolling forward, causing the air velocity on top of the ball to be faster than the air velocity below the ball, pushing the ball down. The opposite is true of the back spin, although you would be really hard pressed to "lift" the back spin serve because gravity is working against the action of the back spin, so unless you put a hellacious amount of back spin on the ball it won't really "lift" all that much. The floater is the no-spin option. People will often compare it to the knuckle ball in baseball. Theoretically, the reason for starting back so far is to ensure that the ball is cutting through as much air as possible, i.e. the longer the ball is in the air the more likely it is to be exposed to the air stream and the more the ball trajectory will change. My personal opinion is that the longer time in the air will psychologically affect the passer more than the aerodynamic effect. the passer has to pay attention to the floater and try to track its path, the longer the passer has to look at how the ball is moving, the more the passer is moving themselves to adjust to the movement, thereby increasing their chances of making mistakes or making an aggressive but erroneous move to the ball which might be difficult to recover from. The jump serve part serves to change the contact point of the serve so that the ball is seemingly coming down towards the passer and forces the passer to react to a different trajectory. By definition, lift is any force acting opposite to gravity. So the backspin ball will have lift. It probably won't have as much lift as it has weight, which means it will still descend. But it will have some lift, so it won't descend as fast as a pure ballistic trajectory. Side spin will make the ball curve sideways ("hook" or "slice", to golfers). Top spin will give it negative lift, making it drop faster than a ballistic trajectory. No spin is a very interesting case, where small perturbations of the flow around the ball will give it a force in a random direction or (best case for the server) first one direction and then another. We had a thread on this a while back which discussed how the ball surface may affect the amount of "float." In baseball, knuckleballers usually want the ball to rotate about 1/4 of a rotation, thus first exposing the stitches on one side of the ball and then exposing them on the other side of the ball. The slower the ball is moving, the longer amount of time it will have to "float." This is why most baseball knuckleballers throw the pitch very slowly (60 mph) compared to fastballs which are 80-100 mph. There have been baseball pitchers who throw the knuckleball around 75 mph, however, with the result being something of a hybrid pitch. How far you start behind the serving line, how hard you hit the ball, how high of an angle you hit it at, and whether you jump or hit it from the ground will all affect the overall trajectory of the serve. So will altitude and air temperature. All of these effects (spin, float, etc.) will be less on a hot day in Colorado than on a cold day at sea level. |
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Post by Reach on Apr 22, 2012 21:56:09 GMT -5
Interesting question. Never thought about it before and wish I hadn't. My mind hurts now.
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Post by vbnerd on Apr 22, 2012 22:49:12 GMT -5
I knew altitude was a factor but never thought about termperature, and probably humidity too.
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Post by mikegarrison on Apr 22, 2012 23:14:53 GMT -5
I knew altitude was a factor but never thought about termperature, and probably humidity too. Humidity has some effect, but maybe more on the weight of the ball than on its aerodynamic trajectory. Altitude is the biggest variable. Aerodynamic forces (lift, drag) are proportional to density. Density will decrease by about 15% from sea level to 5000 feet. Going from 50 degrees at sea level to 90 degrees at sea level only reduces the density by about 7%. The difference between 50 degrees at sea level and 90 degrees at 5000 feet is about 23%, so at least in this regime they are pretty much additive. That killer topspin jumpserve on a cold day in San Fransisco will sail way, way long on a hot day in Denver. Not only will the spin not push the ball to the floor as hard, but it also has less drag. There is a reason why pitchers fear playing in Colorado. Curve balls don't curve as much, and fly balls go farther. |
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Post by Deleted on Apr 22, 2012 23:35:14 GMT -5
If you find yourself in the parking lot, however, take a couple of steps closer.
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Post by mikegarrison on Apr 22, 2012 23:37:30 GMT -5
If you find yourself in the parking lot, however, take a couple of steps closer. |
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Post by head31919 on Apr 23, 2012 0:29:14 GMT -5
On serves from deep, the ball definitely moves more. Step 20 feet back from the line and hit one of the Mikasa blue-and-yellows just right and you can see the ball do some crazy things.
I think it's not as consistently effective as a more traditional floater (or better yet jump float), because you have to hit it harder and if you don't hit it just right it's just a 40mph downball with less spin, but sometimes you will serve a ball that you aimed into the 1/6 seam and all of the sudden the ball is to the left of the left back passer.
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Post by BigTenVball on Apr 23, 2012 7:26:35 GMT -5
i think it was two years ago, but Jim Stone brought a physist to the OTC for HP clinics, and did a session on the physics of serving. was pretty interesting.
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Post by Phaedrus on Apr 23, 2012 7:52:28 GMT -5
i think it was two years ago, but Jim Stone brought a physist to the OTC for HP clinics, and did a session on the physics of serving. was pretty interesting. Yeah, that's Herb, I forget his last name. He was a DI head VB coach years ago in the state of Ohio, I think. I talked to him some this last AVCA convention. In fact, he and I conversed about this very topic about a year ago. Very interesting guy. he works as an accident investigator so he has a lot of experience in the physics of everyday things. |
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Post by Deleted on Apr 23, 2012 7:53:36 GMT -5
Next year they should bring a psychic. I mean, what does it really mean to be the ball?
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