Earth and You: Physics

[stormbind]

Everything on Earth is travelling at the same speed as Earth. When youre in a car, youre moving at the same speed as the car.

But the car is subject to centrifugal forces, momentum, and friction.

Nobody explained the properties of the magical falling man who cuts through the Earth as though it were space dust.

If you were as dense as a blackhole, youd oscillate through the Earth back and forth for a long time, until the Earth was like swiss cheese, like was mentioned earlier. But I think with regular human density and the relatively small acceleration youd get from jumping off a building, it wouldnt be enough to make you pop out on the other side of the planet even once. You probably wouldnt even fall far enough to get anywhere near the core. Especially if you puncture a plate in a high pressure region and magma shoots you back out of the hole like a champagne cork.

That's why I said you would only go a few inches

 

[Mise]

^I thought he cut through matter as if the matter weren't there? So we don't have to worry about displacing the matter, because it stays where it is, and the bloke just "goes through it". So we could reduce it further to a CoM (which is in orbit), and the falling bloke.

The rotation of the Earth would create an extra tangential velocity, which causes it to oscillate as if drawing the outline of the petals on a daisy (I don't know how better to describe it), but suffice to say that it will be "geostationary" with the building the falling bloke jumped from, so that each oscillation will result in the falling bloke starting and ending at the same ledge that he jumped from to begin with.

The orbit of the Earth around the sun would have no effect on the orbit of the falling bloke around the Earth.

That's assuming the properties of the falling bloke are that he goes through matter as if it weren't there.

 

[stormbind]

^ So the falling person is, in the common meaning of the word, ethereal?

Seems pretty silly to apply known science to ethereal beings

 

[G-Man]

Trying to sum up things:
Scenario 1 - No friction: You move without a stop, coming out either where you landed or exactly on the other side (I assume you entered ground vertically) and each time reaching either the top of the building you jumped from or another point at the same distance from the earth's core.
Scenario 2 - With friction: Your movement is similar to the one of Scenario 1, but you're constantly losing energy. As a result you reach a shorter distance from the center of the earth each time untill you eventually stop there.

 

[Bozo Erectus]

Nobody explained the properties of the magical falling man who cuts through the Earth as though it were space dust.

Yeah not enough information. The magic falling person would still need to breathe, as far as we know, so presumably air would remain air and friction with it would eventually slow him down. I think he'd get farther than a few inches though. If nothing but air is acting on his velocity, it would take a while to bring him to a full stop right? If we knew what the maximum velocity of something falling off the Empire State Building was when it hit the ground, and knew the pressure and density of the air at ground level (assuming the airs pressure and density didnt change on the way down) one of the smart people here could probably work out his rate of deceleration.

 

[bobgote]

I think basketcase had it right except for the gravity is constant thing. i was still thinking in terms of friction/resistance forces.

Seriously, Bogdote is correct with his remark:

Bogdote?

 

[King Alexander]

Bogdote?

Sorry bobgote!

 

[Masquerouge]

I say you'll oscillate back and forth, going a little less far everytime, until you stop right at the center of the Earth.
After your first jump, Gravity is pulling you towards the center, accelerating. Without friction, your speed will do nothing but increase.
Now once you pass the Earth's center, gravity will start slowing you down, because now you're headed, thanks to your original velocity, towards the outside of the Earth while Gravity is pulling you to the inside. But you won't go as far as your starting point, just a little less. Then you'll go back to the center, only this time, since your second trip started not as far as your first one, it will take less time (less distance with same acceleration), thus you will achieve a lesser maximal speed, thus your third trip will take you a bit less farther than your second, and so on. Until you completely stop.

 

[BasketCase]

My bad, I just realized I'm completely wrong about my whole bloomin' theory!

If this hypothetical guy goes right through normal matter without affecting it, then gravity can't affect him either! So while Earth orbited the Sun in a CURVED path, the guy would just keep going in a straight line at 70,000 miles an hour, and fly off into space.

Sorry.

 

[Pirate]

I say you'll oscillate back and forth, going a little less far everytime, until you stop right at the center of the Earth.
After your first jump, Gravity is pulling you towards the center, accelerating. Without friction, your speed will do nothing but increase.
Now once you pass the Earth's center, gravity will start slowing you down, because now you're headed, thanks to your original velocity, towards the outside of the Earth while Gravity is pulling you to the inside. But you won't go as far as your starting point, just a little less.

Without friction or anything else to dissipate your kinetic energy, you will reach the exact same height (i.e. potential energy) as when you started. Energy is conserved.

<edit spelling>

 

[ferenginar]

You would just splat on the ground, wall penetrating mode is strictly for walking through walls. If you want to fall into the ground you are going to need ground penetrating mode, which is available on ebay.

http://search.ebay.com/Ground-penetrating-Mode_W0QQsokeywordredirectZ1QQfromZR8

sorry, none available at this time.

 

[Aphex_Twin]

My guess is that if your initial speed were sufficiently great and direction non-colinear to the line linking you to the center of the Earth (COE) you would whizz past the COE at increased speed and continue on a progressively straighter line off into space. If you're too slow you will eventually return to where you started.

 

[EdwardTking]

So you penetrate matter.

But what about radiation?

I rather think that the infra-red from the
molten iron core would properly toast you.

 

[Perfection]

Actually even without friction you would end up in the center of the earth, because your gravity would pull the earth in the direction of your ossilation, eventually imparting your momentum to it.

 

[Souron]

Let's pretend that you jumped off a building, and because of earth's gravity you fall with an acceleration. So you switch into wall-penetrating mode, where now you can fall straight through without being stopped by the ground. What would happen to you in the process? Would you fall out on the other side of the earth? If yes, would you begin to oscillate back and forth between one side of the earth and the other?

You would probobly ossolate as you said.

It is not dissimilar to an orbit exept, becouse you would be going toward the exact center, it is not round but instead a line.

Eventualy your orbit would deteriorate and you would end up in the center of the earth.

 

[Souron]

My bad, I just realized I'm completely wrong about my whole bloomin' theory!

If this hypothetical guy goes right through normal matter without affecting it, then gravity can't affect him either! So while Earth orbited the Sun in a CURVED path, the guy would just keep going in a straight line at 70,000 miles an hour, and fly off into space.

Sorry.

Electromagnetism and gravity are compleatly different forces. Being able to move though matter would mean not being effected by electromagnetic fields.

 

[microbe]

IfI'm curious to know what speed would one's body have(let's say someone weighting 90-100kgr), while he's approaching the core of the earth.

E = 0.5mv^2 = GMm/R

so v = sqrt(2GM/R)

v: the speed at core
G: the universal gravity constant
M: the mass of the earth
R: the radius of the earth

So just put in those numbers and you'll get v. It will be a huge number. And no, the weight of the person (m) doesn't matter.

 

[Mise]

Actually even without friction you would end up in the center of the earth, because your gravity would pull the earth in the direction of your ossilation, eventually imparting your momentum to it.

No, you would both orbit your mutual CoM, which is so close to the CoM of the Earth by comparison with the distance you travelled that it can be ignored. (in other words, if you travel 7,000km, the Earth will travel 1x10^-24m or something rediculously small like that). And I'm not sure what you mean by mentioning momentum... in effect, you will start and end at the same window ledge you jumped from each oscillation.

@Souron:

Eventualy your orbit would deteriorate and you would end up in the center of the earth.

Why?

 

[Pirate]

Actually even without friction you would end up in the center of the earth, because your gravity would pull the earth in the direction of your ossilation, eventually imparting your momentum to it.

If you start high up on a building (high potential energy) and eventually end up at the center of the earth (zero potential energy) where does that energy go? I'm assuming an isolated system of just you and the earth with no friction.

 

[Aphex_Twin]

Actually even without friction you would end up in the center of the earth, because your gravity would pull the earth in the direction of your ossilation, eventually imparting your momentum to it.

And what if initially you are not totally at rest relative to the COE?