/sci/ - Science & Math

iunno maybe lol

What do you mean "stop"? A strand of indestructible material wouldn't "stop" a 747 it would cut the fucking plane in half and fall burning to the ground.

>>6540460
Just assuming that the mass, velocity etc. of the plane were the same but the only difference being that it wouldn't be ripped apart if you threw a lasso of spidersilk around the tailfin

>>6540492
Just assuming Spiderman comes swooping in after his spideysenses were tingling and shoots his spideyweb to lasso the plane and stop it in time to save Mary Jane

>>6540505
Spidey does love his weed

>>6540445
Of course it's true, haven't you ever broken your nose trying to walk through a spiderweb?

>>6540510
No he doesn't. Spider-man in canonical history has never mentioned his love for weed.

>>6540522
>Of course it's true, haven't you ever broken your nose trying to walk through a spiderweb?
The threads in a spiderweb are extremely thin, though. A strand as thick as a pencil might not stop a 747, but it would be pretty strong.

>>6540536
Noses are extremely fragile compared to 747s, too.

Isn't a factor of a spiderwebs strength it's ability to flex though? Like if a big bug flies in it's going to stretch it all over the place and taht tension over time brings the bug to a stop.

However at the speed a 747 goes, would the web even have time to stretch since the material still has the same elasticity at a large scale as it does at a small scale, the larger strand would have proportionally no time to adjust to the high speed and simply be snapped.

>>6540492
> lasso of spidersilk around the tailfin

if it anchored to something with more mass than the plane and the silk has a higher tensile strength than the plain tail, the tail will be pulled off.

If it is anchored to something having less mass than the plane the anchor will be pulled by the plane.

>>6540544
I think if you scaled the nose to the size of a 747 the nose would be stronger. a 747 scaled to the size of a nose would be weak like and aluminium can.

>>6540616
or maybe even as weak as alumium foil

>>6540616
You ever throw an aluminum can through a spiderweb?

>>6540619
not at 500mph

>>6540622
So you think the spiderweb's chances improve under those circumstances?

>>6540625
I dunno can we get some mathematicians on here to scale these objects down and work it out?

nice uts of about 1.4 GPa compared to 500 MPa for steel.
.8 GPa for yield point though (I think. I usually only read metal stress-strain curves).
not even close to stop a 747 though
http://www.wolframalpha.com/input/?i=pi*%28.7+mm%29%5E2*%281.4+GPa%29

>>6540505
>stop it in time to save Mary Jane

but not to save Gwen, huehue

>>6540445
I heard this interesting fact somewhere, but I don't know where. It might be true. I don't know.

>>6540631
It seems to me that you've calculated the force required to break a pencil-width strand of spider silk.

Judging from the Wikipedia article, http://en.wikipedia.org/wiki/Spider_silk#Properties , one would have to apply a consistent force of 2160 Newtons to break that pencil-width strand of spider silk. However, the spider silk is capable of stretching quite a bit. You'd have to apply a force of 2160 Newtons over a distance equal to 30-some% of the length of the strand of spider silk in order for the strand to actually break.

To figure out if a strand of spider silk could actually stop a 747, you'd have to add up all the area under the curve pictured >>6540631 , accounting for the thickness of the strand and the length of the strand. You'd get something like the double integral of pi*(0.7mm)^2 from 0 to (Tensile Str function) and then from 0 to 30% strain; this would give you the amount of Work required to break the strand, which would be equal to the amount of Kinetic Energy a 747 would need to have to break it.

I don't know anything about materials strengths and I'm bad at calculus but you get the gist.

>>6541656
I guess I was looking at it in static equilibrium.
The thrust from a SINGLE engine would easily break the thread.

The kinetic energy of a 747 in flight would be 6 GJ
http://www.wolframalpha.com/input/?i=%28734999+lbm%29*%28300+mph%29%5E2

AND this strand needs to hold up a 735000 lb (sorry units on wolfram) airplane

>>6541673
>The kinetic energy of a 747 in flight would be 6 GJ

That's pretty insane when you think about it.

>>6541656
And now I sorta remember this.
you don't need a double integral you just need to find the area under the curve.
It's easily approximated as a triangle. 210 MPa.
The actual energy absorbed is dependent on the length of the cord as you said. more cord allows for more stretchy.
So 323 J are absorbed per meter.
http://www.wolframalpha.com/input/?i=%28%281.4+GPa%29*%28.3%2F2%29*pi*%28.7+mm%29%5E2%29+in+J%2Fm

So the cord would have to be
18576 km or half the circumference of Earth
http://www.wolframalpha.com/input/?i=%286+GJ%29%2F%28323+J%2Fm%29

I once read that spiderwebs have a thickness:strength ratio stronger than either iron or steel, but I don't remember which.

>>6541782
strength is already independent of thickness as said in >>6540631
Ultimate tensile strength (UTS) is 1.4 GPa vs 500 MPa for a low carbon steel.
Grabbing some new numbers for a high carbon steel.
http://www.matweb.com/search/DataSheet.aspx?MatGUID=cbe4fd0a73cf4690853935f52d910784&ckck=1
UTS is 625 MPa.

Spider strand should be a type of polymer which I believe has a normal elastic region and then a plastic region where the carbon chains are permanently shifted.
If this is true the image in >>6540631 shows a yield stress of around 200 MPa vs 530 MPa for the high carbon steel.

>>6541673
Uhhhhh I don't think you're doing this right. You should be solving for the length of strand needed to withstand that energy. Also:

http://en.wikipedia.org/wiki/Boeing_747#Specifications
>Maximum takeoff weight: 333,390 kg
>Cruising speed: 893 km/h

Formula for Kinetic Energy: 0.5*m*v^2
Kinetic energy of 747 in flight: http://www.wolframalpha.com/input/?i=0.5*%28333%2C390+kg%29*%28893+km%2Fh%29^2
Why do I get 10GJ when you only got 6?

Spider silk
>stress 1.3 GPa
>strain 30% = 0.3

http://en.wikipedia.org/wiki/Pencil#By_size
>6mm hexagonal height
>7mm outer diameter
We'll use outer diameter

Ok, so if I have this correctly, Toughness is the area under the stress-strain curve:
http://www.wolframalpha.com/input/?i=%281.3+GPa%29+*+0.3
1.3GPa * 0.3 = 0.39 GPa

This represents the Energy/volume the material can absorb: http://en.wikipedia.org/wiki/Toughness
A pencil of thickness 7mm has cross sectional area = (pi*(7mm)^2)
Multiply by 0.39: http://www.wolframalpha.com/input/?i=0.39GPa+*%28pi*%287mm%29^2%29

Comes out to exactly 60 kN. This should be the amount of work per meter required to break the strand? So we divide the total kinetic energy of a 747 by this number and we should get the length of strand required to stop a 747:

http://www.wolframalpha.com/input/?i=%280.5*%28333%2C390+kg%29*%28893+km%2Fh%29^2%29%2F%280.39+GPa%29%2F%28pi*%287mm%29^2%29%29

Comes out to 170.8 kilometers, which I feel is a somewhat reasonable answer. For reference, Wolfram Alpha says the thickness of the Earth's atmosphere is 100km.

>>6541840
>Comes out to 170.8 kilometers, which I feel is a somewhat reasonable answer. For reference, Wolfram Alpha says the thickness of the Earth's atmosphere is 100km.
>For reference, Earth's atmosphere is 100km
best reference, jesus nigger

>>6541840
> Why do I get 10GJ when you only got 6?
they're practically the same number.
I got my numbers straight from wolfram alpha
http://www.wolframalpha.com/input/?i=weight+of+747
http://www.wolframalpha.com/input/?i=speed+of+747

> http://en.wikipedia.org/wiki/Pencil#By_size
it's pencil LEAD and .5 or .7 are standard sizes

> 1.3GPa * 0.3 = 0.39 GPa
didn't divide by 2 because the area under is a triangle not a rectangle

This comes out to 300 N as I later said in >>6541752

> reasonable answer

>>6541864
derp I should really reread things before I correct someone
> it's pencil LEAD and .5 or .7 are standard sizes
is wrong should and you're right.
but you need to divide the toughness by 2 because triangle

>>6541699
the power output of a jet plane is pretty insane too. One engine could power a small city

>>6540505
But Spider-Man broke up with MJ and is now involved with a midget after Doc Ock fucked her using Peter's body, so your assumption is already bad

>>6540526
what

>>6540526
>MARY JANE
>RED HAIR

yeah ok.

>>6540622
Why not?