Posted: 7/31/2006 11:16:22 AM EDT
| Let's say man has drilled a hole from the north pole to the south pole. Now, the guy in the north pole ties a rock to a string and starts letting it fall down the hole(lets pretend there is no firery core,just rock all the way thru) when it gets to the equator, what happens? Does it stop? Does it keep going, or does it shoot out the side of the earth? |
Assuming the rock doesn't have enough kinetic energy/ inertia to overcome the pull of gravity on its wa out, it will stop. For all intents and purposes it is going up once it passes the core. |
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Middle school science teacher here. If the rock was lowered into the hole, it wouldn't go any further than the center of the earth. If it was dropped, I suspect it would rocket past the center of the earth but not make it to the oposite surface as a result of drag (air friction). Now, if you can do this in a vacuum, then it might make it all the way through the earth before heading back down. |
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Given your conditions (no fiery core and such), and assuming that the hole traverses the exact center of mass of the Earth, it will procede past the center of the Earth until the force of gravity (now in the opposite direction) stops it and pulls it back the other way. It will then oscillate back and forth, losing some kinetic energy to drag each time, until it finally comes to a stop hovering in the center of the Earth for perpetuity. Unless the crab people take it. CO Edit for speeling. 
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Well.. A) it won't goto the equator..   B) If there is no air resistence, it will fall as fast as gravity will accelerate it, then it will zoom on by the core, be slowed down and pulled back.. ie will go back and forth a while, but each trip will be shorter, then it will stop and stableize in the center... more or less.. |
Give this man the science fair ribbon. 
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......each time the distance passed the center decreases, until it stops. You can copy this by attaching a ball to a string. Hold it out to one side and let go. As it passed the point in the middle it travels less and less away from it until it rests at that point that is closest to the source of gravity. ETA: Crab people! 
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That would depend upon whether or not the hole was drilled along the Earths axis of rotation. If not, then the rock would probably come into contact with the sides, depending of how long it takes to traverse the Earth at terminal velocity (around 200mph). If the hole is on the rotational axis, then the rock will probably not contact the sides. The procession of the Earths rotational axis is likely to slow to cause any trouble there. Again, discounting interference from the Crab people. CO |
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Lots of assumptions to make here. Lets assume no air, lets also assume the hole goes directly through the center, that the mass is perfectly distributed, and the planet is perfectly round. I don't really understand why the string -- but if you use the string to slowly lower the rock, it will stop at the center of the earth. Of course, the weight of the string will cause it to break, so we will have to assume a special mono-fiber string of incredible strength too. The weight of this wiould probably pull the string right through your fingers (literally, and they would drop off into the hole leaving you with bloody stumps) so we have to assume very light mon-filament and VERY strong fingers. A more interesting thing happens if you just drop the rock. Say you dropped it from 3' above the hole. It would appear out of the hole on the other side of the planet, and rise to just a bit less than 3', then fall back in. A while later, it would appear out of the hole into which you dropped it, and rise to a hight a bit less than it did on the other side of the planet. It would keep doing this until the energy in the rock had been converted to heat by the changing gravitational forces, and slowly radiated away from the (warm) rock. |
It is a good tool for troubleshooting problems in an idea. Once you know what your assumptions are, you know what information you need to make an idea make sense. |
Evolution isnt a theory......there is actual proof of evolution and it can be seen........Now it IS a theory when it comes to the begging of life and how evolution started life on earth. When you talk about evolution it is only a theory depending on what context you are talking about. |
This man has the correct answer, even taking into accoun the crab people. Bravo. |
Damnit, DO NOT start this shit in this thread! Take it some where else! CO |
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The rock issue has nothing at all to do with polarity. It's a matter of conservation of energy. The rock starts out with lots of potential energy, and no kinetic energy. As it falls toward the center of the earth, the potential energy decreases, and the kinetic energy increases. At the center of the earth, the rock has no potential energy, but lots of kinetic energy - in fact, a quantity exactly equal to the potential energy it started with. It will continue through the hole until it runs out of kinetic energy. NEglecting friction, that will be when the rock is as far from the center on the other side as when it started out. It will then reverse direction and continue forever. With respect to the magnetic force, the earth would not tear itself apart if it were monopolar. The magnetic force is very weak compared to the intermolecular forces that hold magnetic materials together. |
And I also agree with this answer... www.phys.uu.nl/~strous/AA/en/antwoorden/zwaartekracht.html#v478 |
They will travel the same distance, with or without drag. The acceleration of gravity is independent of mass. (O.K., that's not completely true. The mass of the Earth is so great, though, that the mass of the second object becomes mathematically inconsequential and the acceleration of gravity becomes effectively independent of mass.) My Geek-fu is strong today. CO ETA: The above assumes that you dropped the rounds into the hole, rather than firing them. If you fired the rounds into the hole, the above still holds true when accounting for drag. If you fired the rounds into the hole and assumed no drag on the system, the 5.56mm round would travel farther due to it's greater initial velocity. |
This is right, imagine a pendulum. If you hold it to one side then let it go it will swing back and forth, each swing it doesn't go as far. Eventually it will come to a stop. The same thing will happen to the rock and will eventually stop in the center. |
Uhhhh, no  Try again ? |
You need to read up on gravity and planetary science a bit, methinks. 
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This is the correct answer. |
Guys, think about your question. The earth's axis of rotation IS the shortest path between the North and South Poles. They are poles because of the fact that they are the two points on the surface of the earth at either end of the axis of rotation. Regarding the tilt in the earth's rotational axis: can you feel the tilt? Neither can the rock. Gravity pulls towards the center. Now a question that may throw off this experiment: Is the earth's center of gravity at the midpoint of the axis of rotation? To assume so means assuming that the mass of the planet is uniformly distributed. My guess is that it is pretty close and probably effectively the same, but if there is more mass in one hemisphere than the other, it will affect the travel of the rock. |
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Err.. posted on teh first page dude. I have read the thread.....I wzs commenting to the poster that didnt seem to get that out of it. He said it was rest in the middle. Maybe he ment "come to rest" in the middle. CH |