if an object could fall through the planet,would it start to de-cellerate at half the radius?

Answer 1

actually here the first thing u have to keep in mind is that the more u go below the SURFACE of earth the gravity will DECREASE and NOT increase...so,as it decreases...when we start going away from the centre,the assumed radius gets bigger..and it will start increasing...hence force increases and the object WILL ACCELERATE ....this is a point on which many are not clear...so make it till there...n yes,it was a good question

Answer 2

The gravitational pull of the earth directs all other masses toward its center of gravity. This pull will be weaker the more distance there is between the earth and the mass acted upon, and will be strongest at the earth's surface. However, if an object were to fall through the earth (dark matter, anyone?), then the net force pulling the object toward the earth's center of gravity would decrease as more of the earth's mass ended up behind the object. The object would approach the earth's center of mass at decreasing acceleration (change in acceleration is called "jerk"), but that acceleration would not drop to zero until the object reached the center of the earth, which means the object would continue to gain some speed until it hit the center. So the object would be at its highest velocity as it passed the earth's center, and the process would start again in reverse: The net gravitational pull slowing the object would be weak to begin with, but about the time the object reached the opposite-end surface of the earth (approximate because of terrain variation), the increasing gravitational pull would slow it to a stop and then toward the earth's center of mass again. The result would be oscillation between two polar opposite locations.

That's assuming there's no air or other friction considerations. If you fell through a hole with air present, the friction of the air would cause you to reach a terminal velocity - that velocity would decrease toward the center of the earth because of the dropping net force and the denser air you would encounter at the center. The density of the air and the density of your body would also play a part, so it's actually a lot simpler without air.

Answer 3

Yes, at the surface of the planet the gravitational acceleration is 9.8 m/s^2(that is, the instant you release the object) as it falls, the rate of acceleration decreases (but the object is still accelerating) until it reaches the center of the planet. At this time, the force exerted by gravity now causes it to decelerate at an increasing rate (it is slowing down) until it stops moving and will again be drawn back to the center. As there will be energy loss, it will eventually come to rest at the center of the earth.

Answer 4

It would melt. The core of the planet is rather warm.

If the planet was cold, I think it would fall..... pass by the centre then slowly decelerate as it moved away from the middle, then it would stop (sparkle gently in some eerie subterranian light) and fall back again..... etc... untill it was motionless at centre point. (I suggest a rescue services telephone be installed at this point)

What worries me is, I read the question, and for some reason cant help thinking you were going to drop a spoon into the hole.... yet I have no idea WHY I think it would be a spoon ?

Answer 5

Imagine a tube passing through the centre of the planet, any object falling down the tube would be under the influence of the planets gravity, once the object passed the half way point ( the centre ) gravity would start pulling it back towards the centre which would cause it to de-accelerate and then fall backwards and repeating the process until it became motionless.

Answer 6

In theory it would move in what is called simple harmonic motion. That is it would accelerate until the centre but its momentum would prevent it from stopping .It would nearly reach the surface on the other side then would start the journey back again.Depending on the damping forces the distance travelled each time would get smaller until it eventually came to rest in the centre.Compare with the vibrations of a ruler or spring.

Answer 7

If you mean 'half the diameter' instead of radius, so your talking about getting to the centre of the earth, see the other answers.

If by 'half the radius', you mean half way from the surface to the centre, then it wouldn't decellerate, it would still accelerate toward the centre of the earth because their is still gravity acting toward the centre.

The thing I don't know is whether the force of gravity reduces from 1 G at the earth's surface down to zero at the centre and if so, how does it change with distance from the centre. It would be interesting to know what the graph of force v distance looks like.

For point-objetcs or distant objects like the earth and moon, gravity is inversely proportional to the square of the distance (if you double the distance you get one fourth of the gravitational attraction), but I don't know what it does underground as a lot of the rock that is attracting it is to the left and right, not in its path or behind it.

Answer 8

The object would start to experience a variable force and hence a variable acc. from its journey at full radius and will continue till it reaches centre of the planet where the force and acc. will become 0. It will cross the centre due to its inertia of motion and will start doing SHM( simple harmonic motion) in its further journey as force will act in a direction opposite to its displacement.

Answer 9

aside from the impracticability yes it would accelerate less as it neared the center due too the gravitational pull from the mass behind it

most of the answers ignore the fact that gravity is a function of mass and the mass in front of the object is influenced by the mass behind the object ( and at the center there is not zero G but gravity pulling equally in all directions - the forces do not cancel out they just oppose one another - man schools have really gone downhill )

Answer 10

What makes an object fall is the earths pull of gravity, which is strongest at the center. assuming that the object were able to ignore the mass of the earth and the friction caused by passing through it (nutrino?), then it would only start to decel as it PASSED the earths strongest point of gravity, effectively being pulled back towards the center as it passed.