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Thu Apr 10, 2008 3:20 pm

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Master Masters Athlete
Joined: Thu Apr 10, 2008 3:00 pm
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Location: atlanta

Can anyone out there calculate my release velocity when I threw the golf ball shown in this video?

http://www.youtube.com/watch?v=RDt1JokxdWg

Here are the facts that I do know:
The ball was released at 6 feet off the ground. It travelled 310ft before hitting the ground. The launch angle was 0 to 2 degrees, the ball had a backward spin and reached its maximum height of 20 feet after it had travelled 220 feet. Also, the temperature was 70 degrees, 50% humidity and there was a 5mph tail wind.

So......anyone got the answer?

Thanks

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Roald Bradstock



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Thu Apr 10, 2008 5:06 pm

 
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Joined: Thu Sep 07, 2006 8:03 pm
Posts: 54

Don't you need to know how much time it spent in the air to make that calculation? You are too funny! Love the outfit! Good luck finding the answer!



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Fri Apr 11, 2008 2:03 am

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Master Masters Athlete
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Joined: Sat Aug 26, 2006 2:06 pm
Posts: 192
Location: San Diego

roald62 wrote:
So......anyone got the answer?


But of course.

Just plug in the numbers:

The definitional average velocity formula calculates segment average velocities.

1. Definitional Average Velocity Formula

v = sf - si / tf - ti

where:
1. v stands for average segment velocity
2. sf stands for the final segment displacement
3. si stands for the initial segment displacement
4. tf stands for the final segment time
5. ti stands for the initial segment time

2. Average Velocity Calculations

a) First Segment

1. v = s1 - s0 / t1 - t0
2. v = 0.46 feet - 0.00 feet / 0.024 seconds - 0.000 seconds
3. v = 0.46 feet / 0.024 seconds
4. v = 19.17 feet / second

b) Second Segment

1. v = s2 - s1 / t2 - t1
2. v = 1.13 feet - 0.46 feet / 0.048 seconds - 0.024 seconds
3. v = 0.67 feet / 0.024 seconds
4. v = 27.92 feet / second

c) Third Segment

1. v = s3 - s2 / t3 - t2
2. v = 1.88 feet - 1.13 feet / 0.072 seconds - 0.048 seconds
3. v = 0.75 feet / 0.024 seconds
4. v = 31.25 feet / second

d) Fourth Segment

1. v = s4 - s3 / t4 - t3
2. v = 2.39 feet - 1.88 feet / 0.096 seconds - 0.072 seconds
3. v = 0.51 feet / 0.024 seconds
4. v = 21.25 feet / second

e) Fifth Segment

1. v = s5 - s4 / t5 - t4
2. v = 2.87 feet - 2.39 feet / 0.120 seconds - 0.096 seconds
3. v = 0.48 feet / 0.024 seconds
4. v = 20.00 feet / second

f) Sixth Segment

1. v = s6 - s5 / t6 - t5
2. v = 3.68 feet - 2.87 feet / 0.144 seconds - 0.120 seconds
3. v = 0.81 feet / 0.024 seconds
4. v = 33.75 feet / second

g) Seventh Segment

1. v = s7 - s6 / t7 - t6
2. v = 4.99 feet - 3.68 feet / 0.168 seconds - 0.144 seconds
3. v = 1.31 feet / 0.024 seconds
4. v = 54.58 feet / second

h) Eighth Segment

1. v = s8 - s7 / t8 - t7
2. v = 5.96 feet - 4.99 feet / 0.180 seconds - 0.168 seconds
3. v = 0.97 feet / 0.012 seconds
4. v = 80.83 feet / second

i) Ninth Segment

1. v = s9 - s8 / t9 - t8
2. v = 7.26 feet - 5.96 feet / 0.192 seconds - 0.180 seconds
3. v = 1.30 feet / 0.012 seconds
4. v = 108.33 feet / second

j) Tenth Segment

1. v = sR - s9 / tR - t9
2. v = 8.79 feet - 7.26 feet / 0.204 seconds - 0.192 seconds
3. v = 1.53 feet / 0.012 seconds
4. v = 127.50 feet / second


Full discussion here:

http://www.drmikemarshall.com/ChapterThirty.html

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Ken Stone
http://www.masterstrack.com



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Fri Apr 11, 2008 3:13 am

 
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Joined: Sat Sep 23, 2006 8:24 am
Posts: 202
Location: Utrecht (Netherlands)

Ken comes to a 39 m/sec. My excel for calculating angles and distances in hammer throw comes to 33 m/sec but a hammer is not a golf ball. The air resistance of a golf ball will be more than for a hammer (although even a hammer loses somewhere between 5-10% distance thanks to air resistance), so Ken's answer seems pretty good.
Pretty good technique of you by the way!

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regards, Weia



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Fri Apr 11, 2008 5:57 am

 
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Joined: Thu Sep 07, 2006 4:56 pm
Posts: 105
Location: Houston, Tx

I would think 39 mps is low. That's "only" 87 mph, and 87 mph doesn't produce that sound from a golf ball...at least I've never heard a golf ball do that. Also, that's a pretty average speed for a a major league baseball pitcher and I would expect a jav thrower to be able to beat that pretty easily with a golf ball. One can throw 310 feet with a 39 mps release velocity but you're going to need a launch angle of around 20 degrees and you're going to reach a maximum height of more like 30 feet.

I have no clue about Ken's calculations. Like where he came up with those time intervals and segment lengths. I didn't see any of that in your post, and it certainly couldn't have been obtained from the video. So I'm at a complete loss.

I also am curious how you know all that precise data about angles, spin rates, maximum height, etc. That kind of information is not easy to come by. Also, the angle appears to be closer to 45 degrees than 0. 0 degrees would explain why it only went 20 feet high, but the way you release it and the way the camera tracks, it certainly looks like you threw it up in the air. Maybe your measurements describe a throw other than the one shown in the video?

The lift and drag factors are beyond my little calculator, but I plugged in a 6 ft release height and the angle and release velocity needed to produce a 310 ft throw with a maximum height of 20 ft (in a vacuum), and I came up with ~50 mps (112 mph). In order to make that throw with air resistance you would need to be well over 50 mps. And that my friend, would account for the whirrr.

Next time take a radar gun with you.



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Fri Apr 11, 2008 11:40 am

 
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Master Masters Athlete
Joined: Sat Sep 23, 2006 8:24 am
Posts: 202
Location: Utrecht (Netherlands)

Without thinking whether it is reasonable or not I took 47 m/sec and a considerable air resistance. Then you reach the distance you threw (and without air resistance it would be 222 meters!), the optimal release angle still would be 39 degrees, the apex of the throw 27.82 meters (without resistance 46 m).
You maybe can measure the real release angle from some video-frames? It is well over 20 degrees I think, but cannot see it clearly in the youtubeformat. I could measure it on the original recording maybe. Is it a big file? Otherwise you could send it to me?

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regards, Weia



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Sun Apr 13, 2008 10:50 am

 
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Master Masters Athlete
Joined: Sat Sep 23, 2006 8:24 am
Posts: 202
Location: Utrecht (Netherlands)

Hi Roald, I replied to your mail but it could not yet be delivered. Something wrong? (Slowest mail ever? ;-)
You can find my mail on my site www.at-a-lanta.nl/weia/

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