if a hole is made in the earth from top to bottom and a small stone is thrown, what is the status of that stone
varsh Thurs 24/07/08 14:34
To subscribe to this question you need to
sign in to the AnswerBank or register
if you are not already a member. All you need is a valid email address to register.
|
|
I reckon its status will be that of a low caste stone.
|
|
|
Some people believe that the stone would plummet to the centre then continue for a while before being dragged back to the centre. It would oscillate like this for a while before eventually settling at the centre.
However, it is impossible to make a hole through the Earth and so is a theoretical question that makes no sense.
|
|
|
No chance. The deepest man made hole is about 7 miles. Which is nothing compared to the 25,000 miles of the Earth's diameter.
|
|
|
Good luck. Let me know how you get on. :-)
|
|
|
Just to be sure, could you tell us where the Earth's 'top' and 'bottom' is please?
Also, define 'hole'.
Ta.
|
|
|
Tetjam, the Earth as we know it is only a thin crust on the outside. Most of the planet is molten rock and other plonk. So, as squarebear says, it is impossible to drill a hole right through as it will immediately fill up. In fact, I would postulate that once through the mantle the inside pressure would blow the drill, the drilling truck and the whole drilling installation to kingdomcome.
|
|
|
squarebears answer is correct.
But , as the others have pointed out ; it is a theoretical answer only.
To drill a hole through the Earth is totally impossible.
|
|
|
By the way ! 'Earth' as the planet we live on ALLWAYS has a capital letter E at the start.
'earth' with a small 'e' is the stuff in your garden that you plant seeds in.
|
|
|
Varsh
I assume (unlike the ABers who have answered thus far) that you wish to know what would happen in principle, i.e. a thought experiment. It is irrelevant whether it is possible to drill a hole through the Earth or not. The question is,
"What would happen if there WERE a hole through the Earth ?"
The answer is, the stone would continue travelling until it nearly reached the surface at the opposite side, then fall back towards the centre, and so on, each time not going quite so far, until eventually ending up stationary (and weightless) at the centre.
This of course assumes a spherically symmetric Earth.
|
|
|
Get real! You've drilled a hole through the Earth (I wonder what percentage of the Earth's surface is 'opposite' another piece of land, by the way?) and by some miracle lined it up perfectly with the team digging from the other side and you expect me to believe you're going to throw in a little stone? No way. You're going to be chucking in something that wouldn't look out of place at Stonehenge!
Your little stone is going to reach its terminal velocity so quickly and it's going to get a very disappointing distance past the centre of the Earth before it starts its journey back. Plus use of the word 'thrown' rather than 'dropped' leads me to believe it's going to spend an inordinate amount of time bouncing off the walls, slowing it down even more.
|
|
|
how could that be true nightmare when the earth is surrounded by water?
|
|
|
nightmare is right: this is purely hypothetical question which has nothing to do with practicalities. To refuse to consider it on the grounds that such a hole is impossible is as unimaginative as Fred Hoyle's objection to the idea of monkeys bashing typewriters - he complained that the machines would soon jam up due to lack of oil and then fall to pieces. Give me strength!
I don't know how to solve this without resorting to calculus, which I'll have to brush up on.
The problem is that the 32ft per second per second which we glibly quote as the acceleration due to gravity has that value only at the surface of the earth. As you fall through the earth, more and more of the earth's mass (which is what matters) moves 'above' you, reducing the gravitational force pulling you 'down'. At the centre of the earth, gravity is zero.
So the stone's acceleration will progressively reduce as it falls. Does this mean that it will stop at the earth's centre? What is for sure is that it won't overshoot by very far, if at all.
I think we'd better work it out again...
|
|
|
We could use the hole to disperse some of the excess sea water created by our good friend global warming. That would be a really interesting diving experience. Just a lod of water hanging in the middle of the 'hole'.
When starting in the midlle, I assume that no matter what direction you swam in, it would always be 'up'. A bit like standing on the North pole and only being able to move off Southwards.
|
|
|
If we could put a straight vacuum pipe through the centre of a symmetrical Earth (Okay, so it's a big "if") then the stone would oscillate for ever, except for friction caused by it's being forced against the sides of the pipe by Coriollis force.
|
|
|
Why would it oscillate for ever, Rev?
|
|
|
There would need to be a damping force for it to stop oscillating.
Removing the air would do this in theory.so it would oscillate for ever in the same way that the moon orbits us forever.
However forever is a long time and there are other significant assumptions as well as the practicalities. The Earth is not a perfectly spherical uniformly distributed mass
for example.
|
|
|
Ummm, can I change my answer to "It wouldn't oscillate forever"?
If the pipe contained a perfect vacuum, and if the pipe coincided with the axis of rotation of the Earth, and if the axis of rotation of the Earth were in a constant direction, and if ...etc. then the stone would accelerate as it approached the centre of the Earth, decellerate as it approached the surface on the other side, and oscillate for ever.
In practice, Coriollis' force will always jam the stone against the side of the tube and it will slowly slide to the centre of the Earth, held back by friction.
As you probably know, Coriollis' force is the apparent force which arises because an object will have a certain angular momentum cause by the rotation of the Earth (except at the poles). If you drop the object so that it is nearer the centre of the Earth, the object tries to keep the same angular momentum, but, because it is now nearer the centre of the Earth, its radius is smaller, so the only way that the product of radius and angular velocity can stay the same is for its angular velocity to increase i.e. although the piece of pipe near the stone rotates once in 24 hours, the stone will rotate in 23 hours (say). Consequently it hits the side of the pipe.
|
|
|
Rev, and now jake, I ask again: why would it oscillate for ever? You keep saying so but don't explain.
You could start by calculating (I can't without restudying my calculus) what the velocity (in vacuum) of the body would be as it reached the centre of the earth.
|
|
|
In order to stop oscillating the system needs to lose energy. It can do that if there is air in the tube, the energy goes into making the air warmer, or it can scrape against the side of the tube, again it loses energy by making the tube warmer. There are other ways that the stone can lose energy e.g. if there is a magnetic field.
If there is no way for the stone to lose energy what happens is that the sum of its potential energy (due to its position) and its kinetic energy (due to its speed) remains constant. So if you drop it from the surface of the Earth its initial kinetic energy is zero and its initial potential energy is 1 (in some units). As it falls the kinetic energy (speed) increases and the potential energy (height) decreases. At the centre of the Earth its potential energy will be zero and its kinetic energy will be 1. So it has just enough speed to take it up to the surface again, where the potential energy will again be 1 and the kinetic energy (speed) willl be zero. The cycle then repeats exactly the same.
|
|
Broadband | Broadband | SMS-Sprüche | Loans | Xbox Mod Chip
