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View Full Version : Wind Resistance and Actual Serve Speeds


spikyblackhair
04-20-2008, 07:39 PM
So I happened to flip to Fox Sports Net for a few minutes this afternoon and it happened to be their "Sports Science" show in which they analyze movements in sports. It turns out that according to FSN, the fuzz on a tennis ball and wind resistance makes the ball lose up to half of its initial speed on a serve by the time it reaches the opposite baseline. As best as I can recall, the show explicitly stated that Andy Roddick's 155 mph serve would have been going around 78/80 mph by the time it reached the other player.

I can't do the physics myself, but if this is true, then the difference between a 120 mph serve and a 140 mph serve would only be 10 mph by the time it reaches the returner; a significant difference, but much more manageable than an actual 20 mph difference. The difference between a 120 mph serve and 125 mph serve would be almost negligible. It seems like 50% speed loss is a pretty broad stat, especially when things such as spin and placement aren't accounted for. What are your thoughts?

Gmedlo
04-20-2008, 08:19 PM
While your calculations about the speed of the ball when it gets to the baseline give a different perspective than the measured speed, you have to take into account the total time it takes for the ball to get from baseline to baseline, not just the speed. I imagine the timing is more proportional to the measured speed (initial) than the final speed is.

skierpaul
04-20-2008, 08:23 PM
I think that faster serves loose more speed quicker than slow serves. For example, if you're blatantly speeding at 100mph on the freeway and take your foot off of the accelerator, you will notice an immediate decrease (braking effect) in speed. If you're only going 50mph on the freeway and do the same thing, you'll coast a lot longer at that speed before slowing down. However, in doing this, you'll p1ss off everyone behind you! :twisted:

coloskier
04-21-2008, 06:10 AM
I think that faster serves loose more speed quicker than slow serves. For example, if you're blatantly speeding at 100mph on the freeway and take your foot off of the accelerator, you will notice an immediate decrease (braking effect) in speed. If you're only going 50mph on the freeway and do the same thing, you'll coast a lot longer at that speed before slowing down. However, in doing this, you'll p1ss off everyone behind you! :twisted:

Also being from Colorado, I can accurately state that there are a lot of people ******* other drivers off in Colorado from driving too slow.:twisted:

Freedom
04-21-2008, 06:14 AM
I'm not sure that wind resistance has that much effect on the ball- did the show take the bounce into account? I can believe the bounce would wipe out 50% of the pace...

skierpaul
04-21-2008, 07:56 AM
Also being from Colorado, I can accurately state that there are a lot of people ******* other drivers off in Colorado from driving too slow.:twisted:

You down in the front range? Then you're certainly feeling the brunt of it on the weekends!

coloskier
04-21-2008, 08:09 AM
You down in the front range? Then you're certainly feeling the brunt of it on the weekends!

Weekends? Heck, I get it every day.

snark
04-21-2008, 10:05 AM
While your calculations about the speed of the ball when it gets to the baseline give a different perspective than the measured speed, you have to take into account the total time it takes for the ball to get from baseline to baseline, not just the speed. I imagine the timing is more proportional to the measured speed (initial) than the final speed is.

That's correct -- it is the average speed, which is important.

spikyblackhair
04-21-2008, 10:28 AM
I'm not sure that wind resistance has that much effect on the ball- did the show take the bounce into account? I can believe the bounce would wipe out 50% of the pace...

The show was ridiculously unscientific and pretty much implied that wind resistance was responsible for all of the speed loss.

While your calculations about the speed of the ball when it gets to the baseline give a different perspective than the measured speed, you have to take into account the total time it takes for the ball to get from baseline to baseline, not just the speed. I imagine the timing is more proportional to the measured speed (initial) than the final speed is.

Yeah, the total time from baseline to baseline is definitely more what matters, as opposed to just speed at the point of the return.