this post was submitted on 21 Oct 2024
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[–] geography082@lemm.ee 21 points 1 day ago (6 children)

This confirms Things were more solid in the past?

[–] Krauerking@lemy.lol 31 points 1 day ago

I mean the modern skyscraper is definitely built very different these days.
The world trade center used hollow exterior support so they could avoid having support columns interrupting the floor plans and large central support columns but you can see what happens when the exterior support gets damaged and heat causes sag from the weight.

Advanced techniques usually mean less material and faster build times.
You know what was even more solid? A huge pile of rocks in the shape of a pyramid.

[–] funkless_eck@sh.itjust.works 19 points 1 day ago (1 children)

B-25: 33,000lbs @ 225 mph

vs

767-200: 300,000 lbs @ 500 mph

so, roughly 10x the weight at 2x the speed

[–] pahlimur@lemmy.world 15 points 1 day ago (2 children)

If those numbers are correct, that's 40x the energy.

[–] booly@sh.itjust.works 4 points 1 day ago

40x the kinetic energy. Now consider the chemical energy stored in sufficient fuel for a coast to coast flight of that weight and speed.

[–] funkless_eck@sh.itjust.works 4 points 1 day ago* (last edited 1 day ago)

rough approximation, but I did double check the numbers.

ie we don't know the exact weight of the bomber, but that's its average laden weight, could be lighter without bombs

in 2001 the second plane hit faster than the first and I believe the first is guessed from footage but the second is from the black box?

[–] ProdigalFrog 35 points 1 day ago (3 children)

Possible. Though a B-25 is smaller and much slower than a 737.

[–] Tar_alcaran@sh.itjust.works 16 points 1 day ago

A 767-200, like the one that hit the tower in 2001, carries roughly 3 Fully loaded B-25s worth of FUEL alone.

[–] HK65@sopuli.xyz 17 points 1 day ago (1 children)
[–] frezik@midwest.social 1 points 1 day ago (2 children)

Speed matters more than mass when calculating kinetic energy. A 767 is much, much faster than a B-25.

[–] HK65@sopuli.xyz 2 points 1 day ago

While you're right, the MTOW of a B-26 is around 17 tons, the 767 is 150-200 tons.

So there is a factor of around 10 between them, so if the 767 flies 3 times as fast - which it doesn't, the B-26 cruises at more than 0.35 Mach at close to sea level, and the 767 is not supersonic - that means that the factor from the speed can't be more than about 3 squared, so 9.

So the factors from the weight and the speed are roughly equal IMO.

[–] Anticorp@lemmy.world 1 points 1 day ago (1 children)

Speed matters more than mass when calculating kinetic energy.

Are you sure about that? An air rifle shooting supersonic aluminum pellets has considerably less kinetic energy than a .22 LR bullet, because of the weight of the bullet. Some air rifles actually shoot their projectile faster than a .22, but they have like 10x less energy upon impact.

[–] evidences@lemmy.world 2 points 1 day ago* (last edited 1 day ago) (1 children)

I'm no mathlete but looking up the formula for kinetic energy it's K.E. = 1/2 m v^2 so I'm pretty sure velocity is going to have exponentially greater effect on kinetic energy than mass.

[–] Anticorp@lemmy.world 2 points 1 day ago

I guess it's because of the huge difference in weight that we see such a difference in kinetic energy from pellet guns, even though velocity has an exponential impact on the energy. A standard pellet weighs under 14 grains, and a .22 LR bullet weighs 40 grains. Thanks for sharing the formula though. I didn't realize how huge of a contribution velocity makes for kinetic energy, and I'll definitely look for a faster rifle whenever I upgrade my air rifle.

[–] espentan@lemmy.world 15 points 1 day ago

Not to mention compared to a 767.

[–] MonkderVierte@lemmy.ml 9 points 1 day ago* (last edited 1 day ago)

Not the bomber.

[–] StaticFalconar@lemmy.world 4 points 1 day ago (1 children)

Opposite. This confirms planes back in the day were flimsy as shit.

[–] wildcardology@lemmy.world 0 points 1 day ago

Those bombers back in the day needs to be made of lighter materials so they could carry those bombs and ammos for the . 30 machine guns.

[–] prole@lemmy.blahaj.zone 2 points 1 day ago* (last edited 1 day ago) (1 children)

Different/less fuel I imagine. The problem with WTC was the fires kept burning which weakened the steel enough for it to collapse under its own weight.

Edit: Admittedly, I read the headline as "B-52" but I think the comment stands.

[–] funkless_eck@sh.itjust.works 1 points 1 day ago* (last edited 1 day ago)

yes the B 25 actually lost its engines in the impact that caused two other separate sites with respective fires