Was this ejected rock in a controlled demolition propelled by gravity or explosives?
- Thread starter Hama Neggs
- Start date
Jason
Senior Member
In order for us to ascertain that we would need to know the distance the rock traveled before bouncing off the pavement and at what speed it was traveling.
Hitstirrer
Active Member
It does have some slight relevence to the topic as the vid was put forward to 'prove' that material can be ejected by a gravitational event. Its just a pity that an explosive event was used to display that. In any case nobody here has disputed that material can be ejected sideways from both kinds of events.
However, as you say, it is an interesting mini-topic. But not meriting its own thread. I will put my own 10c forward.
The mystery here is really the velocity of that rock. It sure was hauling ass. If we had access to the raw vid data that velocity would be easier to compute from frame counts. Even that needs an estimation of various distances though.
Starting at that point first. I play golf and that involves much practice in distance estimates. If I was stood by the camera I would select a pitching wedge to hit a green at the base of that large tree seen near where the rock first appears. My feeble skills enable that club to send a golf ball around 50 yards, which is why I would select that club, because that was my distance estimate.
Similarly, if the green was at the base of the right hand building I would choose either a 4 or 5 iron depending on where other hazards were placed. I would then play either a full swing 5 or a 'gentle' 4 club stroke. Both -in my hands- will reach around 150 yards, which is what my estimate is.
As a check there is a rudimentary geometry exercise we can do. The man in the white shirt must be around 6' tall. The tall tree must be around 35' high, and the buildings have to be around 85' high. If you look at the vid that mans eyeline looking at the tall tree would seem to coincide with the top of the building.
Draw a base line of 450' and then a vertical on the left side of 6' and a vertical on the right side of 85'. At 150 ' from the left side draw a vertical 35'. You can then join the top of each vertical with a line- representing that mans eyeline. ( or near enough). This shows that all the guestimates are very close to being accurate. The trees are around 150' feet away and the buildings around 450' - as my golf experience estimated.
Now we have a kind of base to estimate the speed of that rock. Absent accurate timings it is still nowhere near exact, but lets give it a go. The explosion at the base of the right hand building seems to be around mark 7 seconds. The first appearance of the rock is around mark 8 ( late) or early 9 seconds. Then it arrived to nearly decapitate that guy at around mark 10 seconds.
So, if the rock left as a direct result of the explosion it had to travel 300 feet in 2 seconds and then another 150 feet in another second. Consistent.
What speed does that represent? 150 x 60 x 60 = 540,000 feet per hour - or 102.27 mph.
Does that seem consistent with the observation per that video ? I would suggest so.
Now lets look at the claim put forward that the rock began its journey as a result of the building debris hitting the ground. What are the timings for that? Hard to determine of course but I would suggest that from observation it would seem to be late 8 seconds and early 9 seconds.
Here it gets interesting. We have a direct observation of the rock's flight from its first appearance to impact. And we can see that it covered the distance from the trees in around 1 second or 100 mph approx. That means that it had to cover the first 300 feet in another one second in order to have only left when the building hit the ground. Conflict right there.
To have left on bullding impact to the ground it would have to move over the first 300' at double the velocity that it continued once it was observed. (We are into quantum physics now and shades of the 'double slit' experiment ) - ( Observation altering velocity)
My conclusion is that the first hypothesis fits both the observations and the calculations. ie. the rock was launched by an explosive event , travelled 450' at an average velocity of 100 mph and damned near killed a guy.
Can we now close down this interesting sub-topic ?
Last edited:
Jason
Senior Member
For starters, if someone knew where this demo was we could locate it on google maps and then identify the tree line and the street to approximate the distance from the building to where the rock skipped off the street.
TEEJ
Senior Member.
https://goo.gl/maps/Iy5g8
Demolition of once famous cloting factory OP Prostejov in Czech Repubic. Location coordinates 49.4696708N, 17.1369992E
Jason
Senior Member
Wow TJ, how did you find that?
TEEJ
Senior Member.
The video in the OP has the factory name in the description. I just searched on the name and Czech Republic. The coords of the actual building are slightly out. The factory that was demolished is slightly to the north of those coords.
The location where the people were standing.
https://goo.gl/maps/7Duup
https://www.google.co.uk/maps/@49.4...ata=!3m4!1e1!3m2!1s3dry2VuITY9eeD4E4cdJ-g!2e0
Jason
Senior Member
Do you happen to know what the distance is between where they were standing and the demo'd building?The video in the OP has the factory name in the description. I just searched on the name and Czech Republic. The coords of the actual building are slightly out. The factory that was demolished is slightly to the north of those coords.
The location where the people were standing.
https://goo.gl/maps/7Duup
https://www.google.co.uk/maps/@49.4...ata=!3m4!1e1!3m2!1s3dry2VuITY9eeD4E4cdJ-g!2e0
derwoodii
Senior Member.
this was a CT down here 1997 sadly ejected debris kill a girl some 500m away you can see things hitting lake some time after denotation,,, there another vid better showing boats and kayaks getting peppered with shrap but i can not find ATM
skip to 60seconds save ya some time
skip to 60seconds save ya some time
Jason
Senior Member
The initial explosions we here are some sort of fireworks, right? Or smoke "show" because smoke seems to come from the chimney stacks... And then at the end there is another unexpected explosion. Is that part of the show as well, like what they do when they are demo'ing a Casino?
derwoodii
Senior Member.
yes and big trouble, and yes smoke just pyro tech for crowds,,, that they now dont invite to CT events
http://en.wikipedia.org/wiki/Royal_Canberra_Hospital_implosion
http://en.wikipedia.org/wiki/Royal_Canberra_Hospital_implosion
WeedWhacker
Senior Member
I believe you meant 'CD'? aka, "controlled demolition".
But, in comparing this video example to a previous one, we must examine the time elements. The debris in your video show the ejecta immediately after the explosive charges. Whereas another video shows the rock that "almost kills the spectator" arriving WELL after the detonations....and, as already explained, ejecta that is part of the gravitational collapse forces.
Pete Tar
Senior Member.
Not fully confirmed, could be either at this point still.
derwoodii
Senior Member.
yes ops CD
there is mention within vid and report that some debris took some time to land suggesting it went up arc over. A shame I can not find the other vid the perspective is revealing of time lapse from bang to splash
TEEJ
Senior Member.
Hi Jason,
I make it approximately 190 metres. From Google Earth using the ruler in tools.
49 28 28.73N 17 08 31.33E is the coords for the filming area in the OP video.
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