Earth and You: Physics

[stratego]

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?

 

[BasketCase]

Presumably, if the ground isn't going to stop you, then neither is friction from the air. Therefore you will oscillate through the earth forever--probably scaring a lot of people in random parts of the world as your head suddenly pops up through the ground and you go
"BOO!"
at people before disappearing again.

 

[WillJ]

Ralph Nader would become President.

But seriously, wouldn't you just go down to the center of the Earth and stay there?

 

[The Person]

Good question, WillJ. Probably you will bounce up and down for a while before you finally end up in the center of the Earth without any way of getting back up. (And crushed if you turn off wall-penetrating mode.)

 

[King Alexander]

I don't think that the body would have enough acceleration to escape the core of the Earth.

Therefore you will oscillate through the earth forever--probably scaring a lot of people in random parts of the world as your head suddenly pops up through the ground and you go
"BOO!"
at people before disappearing again.

But if you grab a beautiful girl, you will not oscillate alone, you would have a nice company with you! I don't dare to think what "tricks" the gravity would do to both!

 

[stratego]

Ralph Nader would become President.

But seriously, wouldn't you just go down to the center of the Earth and stay there?

Once you get to the center of the earth there'll be no net force acting on you, but you'll have an inertial velocity so you'll be moving.

 

[BasketCase]

But what would cause you to stay at the center of the Earth once you got there? Only friction can do that. Turn friction off, and you have no way to slow down except gravity, which is a constant. With no atmospheric friction, a tennis ball tossed up in the air will land back in your hand with the exact same velocity it had when it left your hand.

 

[stratego]

But if you grab a beautiful girl, you will not oscillate alone, you would have a nice company with you! I don't dare to think what "tricks" the gravity would do to both!

Wouldn't her face just slam to the ground?

 

[BasketCase]

But if you grab a beautiful girl, you will not oscillate alone, you would have a nice company with you! I don't dare to think what "tricks" the gravity would do to both!

Okay, this deserves a moderator-spanking--suggestive language about "bouncing up and down".
I'm shocked, I'm appalled, I can feel my morals being eroded!!!

Okay, more seriously: if you pass right through stuff, you wouldn't be able to grab the girl (which would be really not-fun).

 

[bobgote]

(lets see if i remember anything at all about physics...)

But what would cause you to stay at the center of the Earth once you got there? Only friction can do that. Turn friction off, and you have no way to slow down except gravity, which is a constant. With no atmospheric friction, a tennis ball tossed up in the air will land back in your hand with the exact same velocity it had when it left your hand.

gravity is not a constant. it is relative to distance. just so happens that it is around 9.8m/s^2 on and near earth's surface. you would be pulled into the centre of the earth and remain there.

Okay, more seriously: if you pass right through stuff, you wouldn't be able to grab the girl (which would be really not-fun).

like being stuck in the center of the earth with a girl who is pissed of at you for dooming her to an eternity of your company in the one place WOULD be fun.

 

[BasketCase]

gravity is not a constant. it is relative to distance. just so happens that it is around 9.8m/s^2 on and near earth's surface. you would be pulled into the centre of the earth and remain there.

Actually, we're both wrong.

You fall downwards, into the Earth and towards its core. Until you reach the center, Earth's center of gravity is always below you, so you are always accelerating.

BUT--once you reach the center of the Earth, all the earth's matter is around you, pulling OUTWARDS--and the net force on you is zero. So you go sailing right through the Earth's core and start going up.

At this point, gravity begins to act on you in reverse--you begin to decelerate at precisely the same rate of change as you were accelerating when you were going down. Which leads to the result I originally posted: you bob up to the surface, go
"BOO!"
and start going down again.

(Edit: I like this thread, it's both fun AND a waste of time!)

 

[King Alexander]

Wouldn't her face just slam to the ground?

If you could switch to wall-penetrating mode yourself, why wouldn't the girl do the same?

Okay, more seriously: if you pass right through stuff, you wouldn't be able to grab the girl (which would be really not-fun).

Assuming you controled the wall-penetrating mode, you could grab anything you wanted to: girls, jewelries, etc..., cool!

Seriously, Bogdote is correct with his remark:

gravity is not a constant. it is relative to distance. just so happens that it is around 9.8m/s^2 on and near earth's surface. you would be pulled into the centre of the earth and remain there.

I'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.

 

[stratego]

If you could switch to wall-penetrating mode yourself, why wouldn't the girl do the same?

I have a 35 inch verticle leap. That doesn't mean if I grab a girl, she'll have a 35 inch verticle leap too.

 

[stratego]

gravity is not a constant. it is relative to distance. just so happens that it is around 9.8m/s^2 on and near earth's surface. you would be pulled into the centre of the earth and remain there.

But just because force is zero doesn't mean velocity is zero.

 

[BasketCase]

I'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.

Uhhhh....that depends on the speed you had when you reached the core; forces produce acceleration, rather than speed per se. Once you reach the Earth's core and the planet is pulling outwards on you, evenly in all directions, your acceleration drops to zero and you move through the core at constant velocity.

 

[stormbind]

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?

Presumably there is still a normal force, and presumably still friction between you and the wall of the tunnel you created.

I think you will be a bit like a bunker-penetrating bomb, but due to smaller mass and lower density, you will only travel a few inches before coming to a stop.

What happens to the displaced earth? If you were to oscilate through the earth core, you would in time come to a stop at it's centre.

However, due to the Earth spinning, you would make quite a mess of it (Swiss cheese effect) before gravity has that affect on you.

Also, the Earth is in orbit, and hopefully you are not - so it will leave you behind and the gravity of a larger object (Jupiter, Sun) will be your concern. Are you heat proof too?

 

[Fetus4188]

You would oscilate back and forth if there is no friction, it's not very complicated.

 

[Mise]

However, due to the Earth spinning, [...] Also, the Earth is in orbit

I think there's no friction between anything, and we don't have to worry about the displaced matter. Thus, neither the Earth's spinning, nor the Earth's orbit around the sun will have any effect. (In effect, you are "orbitting" the CoM of the Earth (though the orbit is far from circular ))

 

[Bozo Erectus]

Also, the Earth is in orbit, and hopefully you are not - so it will leave you behind and the gravity of a larger object (Jupiter, Sun) will be your concern.

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.

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.

 

[stormbind]

You would oscilate back and forth if there is no friction, it's not very complicated.

You must have forgotten that there is no such thing as perpetual motion

Stratego did not give sufficient details to suggest that no energy would be lost.