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A question about falling bodies and impacts


Adam Larson CL
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Anyone able to help me understand if this makes sense? A scenario someone proposed and I have reservations about.

A gas cylinder - fill estimated ~170L compressed gas, plus steel cylinder + aerial harness (unclear weight) - is falling. Let's say it hits the upper corner at ~50 m/s, and slows to 30 m/s before hitting the balcony floor. Not shown: the aerial harness with fins are on at first but removed somewhere on the way, left badly crumpled. It's designed so the thing falls nose/valve first. Both the corner impact and subsequent impact through the balcony floor are presumed nose-first, but not necessarily 100% vertical. 
Then somehow its falling causes THE SIDE of the cylinder to impact onto this wire mesh canopy frame, somehow imprinting its clear grid pattern in the paint. We're not sure if the canopy was still erected, or torn down already, maybe crumpled in a corner as seen later. The latter would leave many possible impact angles, most of which would be lower and at weirder angles than this, and with a less rigid grid offering almost no resistance. Anyway, it flips or angles or whatever into the mesh but not along it, then it's mostly nose-down (again or still?) and does its bizarre move to punch a serious hole in the concrete but then doesn't fall through it.  
That last step is also problematic, but it's the mesh impact I need to pin down. As I reason, the movement would have to be sideways so the lateral aspect of the cylinder did not slide on the mesh but it hit perpendicularly.  Is there or is there not any plausible way to have a lateral move into the mesh - with no sliding against it - during or in-between  nose-down positions at the given speeds (again ranging from 50-30 m/s) with an object that heavy?  

Sorry to be the lame science parasite here. I respect science, but never mustered the mustard OR patience to learn the right formulas and apply calculations. I also know amateurs can do it wrong and get useless results. And here we could really use a solid view, not me stumbling around.

I'll check back regularly. more details/explanations available if it helps. Thanks! 

- Adam 

grid marks sequence.png

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You don't have enough relevant detail, but the crux of the matter seems to be if the paint on a heavy object can be scored/etched by an impact, with a pattern from the target of its collision, and I would have to say the answer to that is yes, that can happen.

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Thanks! I wasn't sure if I'd get any bites ever, so this is good.

I don't suppose more info is needed for the core question, but they're available. The imprinting isn't the issue so much as the sideways movement needed (I think) to make the imprint on the SIDE of a cylinder that's otherwise falling nose-down (+/- a few degrees) with some velocity. A key detail is the clarity of the grid imprint suggests no sliding across, just pressed straight into it. Yet its nose is hitting things right before that and right after that.

And there are other possible arrangements for the canopy - set against a wall, torn down in crumpled pile, unclear. But I can't visualize anywhere the cylinder should hit it that way except if it's on the floor and the cylinder tips over forcefully onto it for the final move. What do you think T? Can you think of and describe a scenario that would allow this within the laws of physics? I'm hoping to rule it out, but only after really trying to make it (actually, physically) work.

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46 minutes ago, Adam Larson CL said:

Thanks! I wasn't sure if I'd get any bites ever, so this is good.

I don't suppose more info is needed for the core question, but they're available. The imprinting isn't the issue so much as the sideways movement needed (I think) to make the imprint on the SIDE of a cylinder that's otherwise falling nose-down (+/- a few degrees) with some velocity. A key detail is the clarity of the grid imprint suggests no sliding across, just pressed straight into it. Yet its nose is hitting things right before that and right after that.

As you show it it could be hitting a wall which would rotate it.

 

Quote

And there are other possible arrangements for the canopy - set against a wall, torn down in crumpled pile, unclear. But I can't visualize anywhere the cylinder should hit it that way except if it's on the floor and the cylinder tips over forcefully onto it for the final move. What do you think T? Can you think of and describe a scenario that would allow this within the laws of physics? I'm hoping to rule it out, but only after really trying to make it (actually, physically) work.

When it falls through, it could re-orient itself vertically. It depends on how the canopy tears. It's not prone to giving way all at once - fabrics rip.

There are way too many variables in play to be able to say that it must happen one way or certain things cannot happen. To exclude behavior you have to be able to point to some physical law that prevents that behavior.

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5 minutes ago, swansont said:

As you show it it could be hitting a wall which would rotate it.

 

When it falls through, it could re-orient itself vertically. It depends on how the canopy tears. It's not prone to giving way all at once - fabrics rip.

There are way too many variables in play to be able to say that it must happen one way or certain things cannot happen. To exclude behavior you have to be able to point to some physical law that prevents that behavior.

A good number of variables, yes - not a simple one to be certain of. 

It would shift on first hit, maybe even to flip 90 degrees - which would mean its main velocity is done, tumbled away in side directions, not the best to continue to the next damage. That always was best seen as hit then hit on a pretty straight line. But maybe not.

Other canopty positions: probably none but attached or on the floor could offer enough resistance. Or against a wall, and hits the wall, sideways? 

so if it punches through sideways, canopy attached as shown,  it has to re-orient with no forceful sliding. It could hit straight, bounce back a little, then slide lightly... that's from clarity of the pattern - photo attached (and I don't think it's from full-grid contact anyway - just 2-3 loose bar ends scraping parallel lines when someone moved it - but I'm going with IF SO, then...)

The final impact was calculated to be around 30 m/s to explain its not quite punching through. FWIW I don't think it explains the interior damage very well, as if no single speed can explain all of it. But this damage and the cylinder lying there are the two things considered to decided ~30 m/s, and roughly nose-first. 

So … ruling things in or out entirely isn't needed. The standard I'm curious about - and no rush getting there - is if the side-impact into the mesh is the kind of plausible thing a professional ballistics expert would propose to help prove that it was in fact falling - not as just hypothetically possible but as a matter of reasonable course (is that a phrase?). This is working - test it out a bit in a science context to see if it starts to make more sense or continues to seem pretty implausible. 

cheers

cylinder 2 Reuters 1.jpg

cylinder 2 Reuters 3.jpg

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1 hour ago, Adam Larson CL said:

A good number of variables, yes - not a simple one to be certain of. 

It would shift on first hit, maybe even to flip 90 degrees - which would mean its main velocity is done, tumbled away in side directions, not the best to continue to the next damage. That always was best seen as hit then hit on a pretty straight line. But maybe not.

 

If nobody observed this, you don't know how it happened. Was there a bounce? A glancing blow?

Was there an explosion at some point? It looks like there are burn marks.

Do you even know when the marks were made?

 

Quote

Other canopty positions: probably none but attached or on the floor could offer enough resistance. Or against a wall, and hits the wall, sideways? 

so if it punches through sideways, canopy attached as shown,  it has to re-orient with no forceful sliding. It could hit straight, bounce back a little, then slide lightly... that's from clarity of the pattern - photo attached (and I don't think it's from full-grid contact anyway - just 2-3 loose bar ends scraping parallel lines when someone moved it - but I'm going with IF SO, then...)

The final impact was calculated to be around 30 m/s to explain its not quite punching through. FWIW I don't think it explains the interior damage very well, as if no single speed can explain all of it. But this damage and the cylinder lying there are the two things considered to decided ~30 m/s, and roughly nose-first. 

So … ruling things in or out entirely isn't needed. The standard I'm curious about - and no rush getting there - is if the side-impact into the mesh is the kind of plausible thing a professional ballistics expert would propose to help prove that it was in fact falling - not as just hypothetically possible but as a matter of reasonable course (is that a phrase?). This is working - test it out a bit in a science context to see if it starts to make more sense or continues to seem pretty implausible. 

 Implausible isn't the same as impossible. 

 

You can flip a coin and have it come to rest on its edge. It's implausible for any one toss, but it happens.

 

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32 minutes ago, swansont said:

If nobody observed this, you don't know how it happened. Was there a bounce? A glancing blow?

Best explanation to make it fit - not entirely specified. Chipped corner, (attached, w/some context reveal), then canopy something (no one's certain where it would anchor), the clear side imprint something, final hole punch and tip over something. It's all a bit mumbly, IMO, but I'm trying here. Canopy imprint is the current idea I'm tracing and assessing. The required movements and plausibility thereof. All the related parts are physics interesting too, and I'm happy to discuss it all. I just don't want to go off... 

"Was there an explosion at some point? It looks like there are burn marks."
Some thought so, but ... officially no, in the proposed scenario. The fire inside is different - a lit fire, reason unclear. Otherwise, opinions differ. That is some bent rebar. But then as they point out, that intact bit could be where and why the cylinder stopped.

"Do you even know when the marks were made? "
The grid-like marks? I think they were scratched before the fire was lit, from the way its soot seems to catch extra on the lines there. Apparently then before it was moved around that we know of. Logically, it got the marks in the course of arriving at that spot. And opinions differ on how it got there. Some say it was placed by hand, next to unrelated explosives damage. Others say it fell from the air, though they don't say how it began falling.

"Implausible isn't the same as impossible. You can flip a coin and have it come to rest on its edge. It's implausible for any one toss, but it happens."
If it's remotely comparable to that ... I'm feeling vindicated in my doubts. Some people have been like "well, of course," and some competent expert proposed the idea. And maybe so, but ... maybe not their best call.  but no one can illustrate it, so I had to make that image as a best guess or start point at one.

fragpat4.png

Edited by Adam Larson CL
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  • 2 weeks later...

Let me put my understanding of the situation to you. Two things seem given:
First, the deformation on the cylinder suggests contact between the side of the dome and an obstacle.
Second, the almost circular shape of the crater requires a vertical impact or explosion.
At 30-50m/s the cylinder moves relatively fast. Anything that hinders its path in this movement but does not deflect it can only cause longitudinal scratches, but no lateral imprints.
If the cylinder actually fell, it was stopped by the balcony, because it did not fall into the lower level. The only way to get from that vertical standstill to a lateral contact is to tip over onto the grid. In this case the the force wouldn't be sufficient. Furthermore, the grid would have to be next to the crater with the cylinder on top of it.
A bounce or a lateral contact against the wall can be excluded, because such a contact would have left considerable / visible damage. Except for the fragment patterns from any explosion, however, no damage can be attributed to the cylinder. Furthermore, the bouncing should have taken place after the formation of the circular crater, because (as we know from hole at location 4) this bounce can only happen to a very small extent and the energy after bouncing could neither create such a crater nor damage a bed. Even if enough energy would remain the lateral bouncing cylinder would certainly not create a circular hole of its double diameter without more excessive damage to the surrounding walls first.
Therefore, the assumption that these scratches were created as lateral bumps on the way between the roof corner and the crater (or even after the creation of the crater) is similar to squaring the circle.

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Hi, Michael! I was about to come back and bump this, hoping for more thoughts from the existing community. But this couldn't hurt in that, and it's another thought in this science-based discussion.

Concerning the idea quoted below (I can't type below it), you don't see it at possible to hit the lattice (as needed) in between its nose-down impacts? That seems all but required for the scenaio.

Does anyone else have a thought on this? What might be useful is a best effort to explain such an impact - it's not impossible, so what factors would make it possible enough to just happen?

Quote

The only way to get from that vertical standstill to a lateral contact is to tip over onto the grid.

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