You calculated the size of the hole wrong, it's based on radius, not diameter.
My bad, thanks for pointing it out. That should reduce the result by a factor of 4 or 3169200 Joules for the ceiling destruction.
Assuming it's a 15 cm thick reinforced concrete slab sounds like a bad assumption. I wouldn't expect the ceiling to be much more than 5 cm thick, and I'd expect it to be ordinary concrete
We don't use ordinary concrete for roofs, beams, pillars supporting structures etc. Once we we get into multi storey building roofs, they are always reinforced with other materials and steel bars, because concrete has low tensile strength and tend to bend and crack easily without support. This however doesn't mean ordinary concrete is weak though since it has very high compressive strength and is widely used in making roads and pavements where u need not worry about tensile strength too much.
Also, 10 cm is usually the minimum standard thickness for concrete slabs and mostly used in small residential buildings where the support requirements are lower, while 15 cm or higher are used in commercial areas or large open rooms or roofs without much beam or pillar support. 5 cm is way too low even for RCC slabs let alone ordinary concrete.
So, I'd say my assumptions were modest in that regard.
I think we just can't see fragments because the camera's so far away, and the panel's so small that it has to be stylised, so v. frag would be safer for cleanly going through.
Well u do have a point.
However, considering the fact that the ball should already be hitting with multi mega joules of force on the wall, the destruction level even according to the scans (which looks like dust without much of fragments visible) seem consistent for pulverization.
Moreover, in the next panel we can literally see explosion/smoke effects upto outer space which haven't even dispersed(which easily suggests the feat's time frame should be in the order of couple of seconds at most rather than minutes, essentially proving whatever we have calculated is orders of magnitude less).
So I'd say even pulverization seems a safe assumption.
But in the end, if we add total K.E we get 9563626 + 3169200 = 12732826 J or 9-B+. So, I guess it was an effort in futility
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I'd still argue these dimensions are far too vague to reliably use for the feat.
Yeah, just waiting for the anime to get Tier 8 AP and MHS speed seems a better option.
I did try to keep as few vague assumptions as possible. The building itself looks multi storey, so I haven't accounted if there could be the presence of multiple floors, or extra beams for support or that there are other materials being used on top of RCC ceiling(after looking at other panels in the chapter), or that the top roof above the building itself could also consist of metal sloping roofs etc. But I don't want to go that deep into it.
I thought just taking a normal RCC ceiling with the minimum standard thickness for such large open roof without support should be a safe enough option.