Please explain what will happen?

Question

Hi, please could you tell me what would happen in this following situation.
A hole has been drilled though the diameter of the earth which is 0.5 Meters wide. (I know this is impossible but lets say it is). If a coin, was dropped in this hole what would happen?
This may seem simple, but I do not know what would happen. Would the coin stay in the middle, or would it fly out of the other side? I think that it could not fly out of the other side as the momentum would not be enough. (Newton Ball idea)
Please explain to me what would happen. This is just a random question, I am just curious to find out.
Thankyou.

Answer 1

So, you have a straight-line tube through the Earth. Let's say the tube has no air - it's a perfect vacuum also.



At the surface, you drop a coin into the tube. At the surface, the gravitational pull of the *whole Earth* pulls on the coin, accelerating it. (It's no different than if you simply dropped the coin on the ground.) The coin will continue to drop and accelerate, as the mass of the Earth continues to act on it.



As it's falling, the *rate* of acceleration begins to dwindle... why? Well, the deeper it falls, there's less of the Earth's mass below it, and more of the Earth's mass above it. When it reaches the center of the Earth, then the amount of mass below and above it are equal; It's acceleration stops, and the coin is moving at it's fastest here.



Now, there is more Earth on *this* side of the coin, and less in the direction it's moving... so, it begins to decelerate. As it continues it's journey, the speed grows less and less, as there is more and more of the Earth's mass pulling on it.



Your friend is waiting at the other end of the tube through the Earth, and he sees the coin approaching. It continues to slow, and just as it reaches your friend, it pops up out of the tube just about to the same height you held it when you dropped it *into* the tube on your side. He reaches out to grab it - but misses... it falls back into the tube - and repeats the journey back to you, accelerating to the center of the Earth, then decelerating, then popping out to your side, where it halts it's motion again...

Answer 2

Assume your hole is a vacuum (absence of any frictional forces) and the earth stopped turning (to keep the coin from bouncing off the wall due to coriolis forces. The gravitational pull on the coin at the earths surface is 9.8m/s^2. The gravitational pull of the earth is given by G*M1M2/r^2 where r is the distance from the center of the earth. As the coin drops it is continually accelerated but by a lesser and lesser amount as it approaches the earths center where the acceleration becomes zero. At this point the coin will have high kinetic energy so it will keep going until the kinetic energy is turned back into potential energy which, assuming no friction etc, will be when the coin appears on the other side of the world. You might ask, as the coin approaches r=0 why isn't the gravitational force getting bigger?? The answer is that as the coin approaches the center of the earth M1, the attracting mass, is also becoming zero. The attracting mass is only what is inside the current location of the coin as it falls and is proportional to R^3----so as the coin falls the force of gravity becomes G*(k*r^3)*M2/r^2 or the gravitational force is proportional to the current radius of the coin----or zero at the center of the earth.

Answer 3

If there was a vacuum in the tube then the coin would fall at an increasing speed until passing through the center. Then it would "fall" up the other side slowing down until reaching the same height out the other side that it was dropped from. Then it would fall back and repeat, indefinitely. Assuming a perfect vacuum. If the tube was not a vacuum then it would not fall as fast due to friction with the air in the tube, then it wouldn't "fall" up as high out the other side also due to friction. It would fall back and forth around the middle in decreasing amounts until eventually it came to rest in the middle where there is no gravity.

Answer 4

Under frictionless ideal conditions for a non rotating earth the coin would accelerate to the centre of the earth and then decelerate until it reached the surface at the other side then fall back and continue oscillating like this forever.



A rotating earth adds a complication in that the coin has motion imparted by the spin of the earth. This would cause the coin to hit the side as it fell.

Answer 5

you will get either of 2 answers depending whether person believes newton of einstein



Einstein says that gravity is an effect, the result of a distortion of space/time caused by the mass of an object



In the case of the earth

the mass of the earth causes a distorting of space/time

(the analogy of the ball on the rubber sheet)

That distortion is fixed no matter where you are relative to the distortion (provided your mass is negligible relative to the mass of the earth)

(in the analogy- if your mass is negligible then no matter where you are on the sheet, the "dip" in the sheet is fixed cos its caused only by the mass of the ball, and THAT dont change.)

THAT means that as you get closer to the centre of the earth you get closer to the lowest point in the "dip"

Since this is the point of maximum gravity then you will experience maximum gravity at its centre (cos the only way you can go from there is up the sides of the "dip" i.e to lower gravity)



That is

the coin would accelerate after it was dropped, and this acceleration would increase as it got closer to the centre of the earth, then start to decelerate as it went past

i.e it would continue as robert D said

Answer 6

It hist the side of the tube as it falls due to changes in angular velocity, when it starts falling it has the angular velocity of the surface it rests on - so it bounces from wall to wall losing energy.

It will overshoot the centre and repeatedly fall back.

If air is present in the magic tube then it arrests pretty quickly at the centre.

Answer 7

Gravity is exerted from all around earth to wards the center, where here it is at its fullest force. So the coin will stay there in the center of earth (allowing there is no magma and high temperatures that would melt it and turn into a liquid state or even a gaseous state.)

Answer 8

That's the premise behind the Gravity Train and it's also why the ISS orbit is 90 minutes.

Answer 9

Sorry but im to lazy to read wat ever the hell you wrote sorry