Yoku Wakaranai Keredo Isekai ni Tensei Shiteita You Desu - Vol. 16 Ch. 75

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I blame Triella. She had to go and confess, which we all know is a death flag.
 
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No its the same as the wn too.
So I went to look up that chapter again, and you're right. Though in the WN it's really truncated compared to the manga, so I guess I forgot. There was no special version of her burst dagger, and the attack on her by the giant was much more casual. A lot of details about this battle were quite different really.
 
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There is zero chance she is actually dead. She is gonna revive or get saved or something, i swear
 
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Until I see the appropriate markups, I don't think Ren is dead.

Anyways, how the hell does a giant acquire a powerful ice spell and manage to be as stealthy as a house cat?
 
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so there is no waste energy aka back blast.
Backblast is not wasted energy, backblast is an unfortunate consequence of the third law. It would be impossible to push the icicle as high up without having an equal amount of energy directed in the opposite direction.
 
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When the giant lifts his foot a piece of written cardboard can be seen in the indentation in the ground.
It reads: "I aten't dead."
 
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That giant has got to have a stealth skill or something. He keeps catching people off guard while being big and slow.
Since when does BIG=SOW?

Because he's big, he can probably cover hundreds of meters in a single step. Because he's big, those massive muscles can accelerate his body at a speed not possible for tiny humans. Because he's big, even slow movements proportionally speaking are actually fast.

It's like when you watch a big airplane coming in to land and it looks like it's just slowly and gently floating in the air. It's going as slow as it safely can - about 160mph - faster than the top speed of most cars.
 
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Backblast is not wasted energy, backblast is an unfortunate consequence of the third law. It would be impossible to push the icicle as high up without having an equal amount of energy directed in the opposite direction.
If we want to be strict about it, using 'backblast' to refer to the omni-directional explosive heat and kinetic energy of the device itself is technicallyan incorrect use of the term.

As far as a shaped charge is concerned, any energy not being directed in the 'shaped direction' is waste energy. We don't need to assume whether it's possible or not in the setting, as Ren's whole reason for making this a special version of her burst dagger is so there is no collateral damage in the damage of the town. Typical shaped explosives redirect as much energy into the desired direction as possible (though usually not all), and Ren has done it through magical means so we can assume it's 100% efficient. In reality, it's possible because Newton's third law as far as the clause "opposite direction" is concerned only applies in a perfectly elastic and two dimensional physics model.
 
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it's possible because Newton's third law as far as the clause "opposite direction" is concerned only applies in a perfectly elastic and two dimensional physics model.
If you draw a plane through the point of reaction (in this case, the epicenter of the explosion), splitting the resulting force vectors into those on one side of the plane (a1...an) and those on the other side of the plane (b1...bm), the sum of vectors a1...an will be the opposite of the sum of vectors b1...bm. Or
png.image
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vectors.png

Perfectly elastic or not, you're not getting rid of b1...bm no matter what, and so things will shoot towards the ground as violently as debries from the icicle will fly up.
I will buy the explanation of "it's magic, so the law of conservation of energy does not apply, and reaction forces magically disappear". I will not buy the explanation that it is about efficiency, shaped charges throw as much stuff and with as much force in the direction opposite to that of the jet stream, the only things special about shaped charges is that jet particles don't deviate much from the intended direction.
 
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shaped charges throw as much stuff and with as much force in the direction opposite to that of the jet stream
This is false, isn't it. If by "stuff" you actually mean mass, then less mass may be accelerated to higher velocities or more mass may be accelerated to less.

Which is significant in the case of the icicle scenario because on one side of the explosion we have icicle and on the other side is only air.

We must agree that the backblast must be as energetic as the ice fragments soaring upwards. But that energy does not necessarily translate into equivalent amounts of "devastation." And the argument w.r.t. "devastation" is one of strategy and not physics. But I disagree that the sound and heat energy distributed across the city below is as devastating as the ice mass that could have impacted it.
 
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This is false, isn't it. If by "stuff" you actually mean mass, then less mass may be accelerated to higher velocities or more mass may be accelerated to less.
I misspoke when I said "as much stuff", but that's what I meant, yes.
But I disagree that the sound and heat energy distributed across the city below is as devastating as the ice mass that could have impacted it.
"Sound energy" is underselling how destructive a shockwave can be, especially from an explosive that evaporated most of the ice mass. In fact, we can estimate the heat energy that went into evaporating the icicle alone, even disregarding the kinetic energy that went into breaking and propelling the icicle upwards, it is gonna be a whole lot of Joules. From that, we can look up how much TNT would it take to create an equivalent explosion, and use Kingery-Bulmash to estimate the shockwave.
 

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