If u were to make a hole straight across the earth what would happen if u free falled down?

I'm going to have to disagree - nowhere does anybody say that the air was sucked out of there. Heat considerations aside, you'd maintain your angular momentum with the Earth, and the effect of the Moon would be negligible, however you would not enter simple harmonic motion. You would begin a dampened oscillation, going a little bit less closer to the surface ever time due to air friction slowing you down. You would eventually come to rest (more or less) at the gravitational center of the earth. You would then essentially be in free-fall, like astronauts.

Actually, this is a traditional mechanics problem that you will see in an introductory physics course. The moon's gravitational pull is typical neglected and if the hole is drilled long the axis of rotation there is no contribution from Earths rotation.

Assuming you wont burn up in earth core:

If the hole is drilled directly through earths center (along the axis of rotation) when you jumped down it you would enter into simple harmonic motion about the center of the earth. This can be proved mathematically using newtons universal law of gravity and Hooke's law.

The best way you can picture this without all the math is to image the gravitational force originates from earths center. So once you pass it you will be pulled back toward it. Then you will pass it again and you will be pulled back toward it again. With no air Resistance this will continue forever.

You would be deep fried....Ha ha...where does gravity begin is a good question since if you drill a hole thru the earth you must fall from both ends towards the centre if you jumped at either end.So if you jumped and accelerated at 10 m/s per second you would reach a very high speed before 6373km were up at the centre and it would be very hot unless the hollow planet theory is true .Basically science has a theory on it but whats in the middle of the earth is a mystery

let's say you don't die (somehow)

if it's drilled along the rotation axis then you'll bounce up and down (but you wouldn't know which one is which) until the friction with the air and gasses (which will be filling the hole) stop you. You'll then be in free fall at the center of the Earth but you'l still be affected somehow by the Moon's gravitational field.

If it's not drilled along the rotation axis it will hurt you... you'll lose speed a lot faster because you'll be hitting the sides of the hole as the Earth turns...

Don't try this at home kids... ;)

You would die! Lack of oxygen would kill you because the earth is full of gases. The shear speed would of the fall would kill you or you can just say the heat would do that too. If you study what the earth is made of and at what depths the sub-ducted crust begins to melt you will realize that we can't make it very far before we would die. The movies will make a young person think that we can go to the middle of the earth or that we have made it very far into the earth, but we have not and can't. If you want to eliminate all those factors then you would eliminate earth being earth and that would not create much of a scientific question at all.

If you jump , till you reach the centre of the earth you will be accelerating. once you cross the centre retardation starts.till your velocity becomes zero. Again starts falling towards thge centre. It is getting repeated. and finally you will be oscillating in the hole vertically and finally you will be coming to rest.

This is only an imagination. because the core of the earth is the molten lava. and what all things I said will not happen.

If you fall down the hole dug straight across the earth, you would only be staying at the exact center of the earth because that is where gravity is concentrated. It is where the earth will pull you to.

I also assume that u don't die due to the heat.

In that case, u will execute a simple harmonic motion about the centre of the earth.

I would have provided the proof, but I know others ( who have previously posted answers to the question) know it too & they have not posted it due to some reason. Probably u are a little bit small now, u'll see the theoretical proof, once u become promoted to 12th std.

I am loving that you are so intelligent for 14! Loving it! I hate math!

I was thinking that yes you may free float at some point but what would happen if you reached the core? Would you just be stationary at a certain level or would you reach the core and burn?

If the hole is drilled directly through earths center when you jumped down you will be oscillating from one end to other end

continuously