#1
I thought this was interesting:

http://www.youtube.com/watch?v=FAFUSbIs5KA

Basically, it's a hypothetical situation where an underground tunnel connects two cities and the force of gravity pulls you toward your destination for half of the ride and slows you down for the other half. Air friction and stuff would obviously cause issues and stuff, but it's just a cool idea.
#4
the only way that would work is if the tunnel was a vacuum and you used electromagnets to guide the vessel in place without actually touching anything. but you'd be screwed if anything went wrong.

and where does all the displaced magma go?
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Quote by element4433
Yeah. people, like Lemoninfluence, are hypocrites and should have all their opinions invalidated from here on out.
#6
Quote by Firzen_Zero
I'd not be worried about air friction. Rather about err... pressure and heat.


Lol true. I was just talking about air friction slowing you down and stuff.

For this idea to work though, it doesn't necessarily have to go through the center of the earth though. It could be like this:

#8
Maybe I'm misunderstanding this but why would it generate a lot of Gforce?

if anything you'd feel zero g on the journey to the center and 2G on the upward journey.
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Quote by element4433
Yeah. people, like Lemoninfluence, are hypocrites and should have all their opinions invalidated from here on out.
#10
Quote by Lemoninfluence
Maybe I'm misunderstanding this but why would it generate a lot of Gforce?

if anything you'd feel zero g on the journey to the center and 2G on the upward journey.



no, i dont think you'd ever feel 2g. as you travel towards the center you will feel a net force of g->0, and then 0->g on your way out.

and you'd never really feel more pressure (I THINK) than 9.8N acting on you since the earth isn't gaining mass as you're travelling through it, and once you're inside the earth you can't really use the center of the earth as the source of the gravitational force anymore.

(I THINK)
#11
that is interesting, that dude seemed pretty stoked about it lol.

Now I'm watching the Celebrity Skin from the related vids...
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#12
Quote by Zida
no, i dont think you'd ever feel 2g. as you travel towards the center you will feel a net force of g->0, and then 0->g on your way out.

and you'd never really feel more pressure (I THINK) than 9.8N acting on you since the earth isn't gaining mass as you're travelling through it, and once you're inside the earth you can't really use the center of the earth as the source of the gravitational force anymore.

(I THINK)

actually yep. I think you'd feel a maximum of 1G
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Quote by element4433
Yeah. people, like Lemoninfluence, are hypocrites and should have all their opinions invalidated from here on out.
#13
the question of life, the universe and everything.... is 'how many minutes would it take me to get from one side of the earth to the other if i were to travel in a straight line'

..... amazing...
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#14
Electro magnets powered by a cable connected to an orbital satilite and ground station would create a tunnel through mantle, even guide vehicles.
But with all taht energy, you could more easily power every other form of transportation.
...
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#15
Quote by toaster_poodle
that is interesting, that dude seemed pretty stoked about it lol.

Now I'm watching the Celebrity Skin from the related vids...


There's an 8,000 mile void I wouldn't mind jumping into...
#16
Oh, and you guys have NO understanding of G force.
The world's largest roller coasters produce a force of 5 G.
That's at 86 miles per hour.
Going the speed in which 42 minues gets VERY high G-forces.
...
Please do not insinuate anything sexual from that.

Quote by cobain_is_king
If your friends don't like your guitar, cover it in stickers and it'll be teh rawks!
#19
Quote by fretsonfire74
The G forces and heat generated would be phenomenal.


Quote by Zida
no, i dont think you'd ever feel 2g. as you travel towards the center you will feel a net force of g->0, and then 0->g on your way out.(I THINK)


Quote by Lemoninfluence
actually yep. I think you'd feel a maximum of 1G



Actually... the G-Force in this case would be 0 G for the first half (since the capsule is in free-fall), and then 2G during the second half of the journey. Zida and Lemoninfluence you have the right thinking, but you have to use vectors to calculate this. I'll explain below.


Facts:
- An object at rest is 1G
- All objects fall at 9.80665 m/s² regardless of weight.
- 1 G = 9.80665 m/s².


Since the capsule is falling towards Earth's center of gravity (down = negative in vector calculations) we have -1G (-9.80665 m/s² + 1G (the object) = 0 G.

When the capsule passes the center-point of gravity we have the following: +1G (+9.80665 m/s² + 1G (the object) = 2G.


So the second half of the journey is actually at 2G.
#20
Quote by Four Symbols
Actually... the G-Force in this case would be 0 G for the first half (since the capsule is in free-fall), and then 2G during the second half of the journey. Zida and Lemoninfluence you have the right thinking, but you have to use vectors to calculate this. I'll explain below.


Facts:
- An object at rest is 1G
- All objects fall at 9.80665 m/s² regardless of weight.
- 1 G = 9.80665 m/s².


Since the capsule is falling towards Earth's center of gravity (down = negative in vector calculations) we have -1G (-9.80665 m/s² + 1G (the object) = 0 G.

When the capsule passes the center-point of gravity we have the following: +1G (+9.80665 m/s² + 1G (the object) = 2G.


So the second half of the journey is actually at 2G.

That is a gross oversimplification.
#21
Quote by Iansmitchell
Oh, and you guys have NO understanding of G force.
The world's largest roller coasters produce a force of 5 G.
That's at 86 miles per hour.
Going the speed in which 42 minues gets VERY high G-forces.


The earth moves through space at 18.55 miles per second. By your logic, we would feel 3882.5 G just standing here on earth.

G force is related to acceleration, not speed. You would only ever feel 1 G since you are only being accelerated by the earth's acceleration of 9.8 m/s^2.
#22
Quote by Iansmitchell
Oh, and you guys have NO understanding of G force.
The world's largest roller coasters produce a force of 5 G.
That's at 86 miles per hour.
Going the speed in which 42 minues gets VERY high G-forces.

You're saying that high speed will cause high G-Force -- that is not necessarily true (and completely wrong in the case of the posted hypothetical situation). G force has NOTHING to do with speed. It has everything to do with ACCELERATION.

The roller coasters you speak of often have abrupt turns which can cause high LATERAL acceleration, and thus high LATERAL G-Forces. They never cause anything more than 2G for vertical acceleration. This is of course assuming that they don't use any additional energy to the kinetic energy from the first fall (which is the case in most roller coasters).

So while you would travel VERY fast after 42 minutes at 9.8 m/s² acceleration (since this example runs on just free-fall due to gravity) -- you still don't ever experience anything more than 2G (and that's during your trip past the center-point of gravity). This is because (as mentioned before) G forces are determined by ACCELERATION, not speed. The speed is always increasing, but the ACCELERATION remains constant. Thus the G-Force remains constant. Technically, you experience 3 different forces. 0G on the first half, 1G during a split second as you pass the Earth's center of gravity, and 2G on the second half.
#23
I don't think that you ever would feel 2g like you guys are saying. Even though you are decelerating from a high speed, your acceleration is always 9.8 m/s^2 which equals 1 g.

I'm almost positive that you would feel exactly 1g at both the start and stop of your journey, and closer to 0g as you move closer to the center of the earth. Because at the center of the earth, all forces on you are balanced.
Last edited by Brain245 at Jun 14, 2008,
#24
^ It can't be 1g at both the start OR the stop because 1g is when an object is sitting still. An object in free-fall (weightlessness) is always 0g -- I never say I'm 100% sure on things, and don't mean to be an ass here, but I'm 100% sure that it's 0g during the first half (assuming its in an exact free-fall of course).
Last edited by Four Symbols at Jun 14, 2008,