why is the gravitational field of an object dependent on the mass density rather than the mass of the object?

Answer 1

The "gravitational fields" of an object does depend somewhat on the density of the object, but obviously it also depends on the mass of the object.

The reason I say that the gravitational field of an object depends somewhat on the density is because the denser the object, the more compact the object is. Since most of the mass is concentrated near a very small region of space, the gravitational fields of the object near its surface will be very dense, or very strong. On the other hand, if you had an object with the same mass, but it is very large, so that the mass is ditributed over a very large region of space, then the gravitation fields of the object near its surface will NOT be so dense, and therefore not very strong. (To summerize: the mass of an object determines how much gravitational fields it has, but the fields can be distributed over a large volume or a small volume of space. Therefore, the density of the object determines how close together or how far apart the fields are; hence, determines how strong or weak the gravitational pull is.)

A good example of this is a blackhole, where it is so dense that near its center, there is a point where not even light can escape its gravitational field, because it is so dense and strong.

Answer 2

It isn't, it only depends on MASS and DISTANCE. If you are 4,000 miles from the center of the Earth, like we are now standing on the ground, gravity is 1G. If you are 8,000 miles from the center of the Earth, which is the same as 4,000 miles above the surface, then gravity is 1/4 G. It would not matter at all of the Earth were compressed to one inch in size, that would still be true. But if that were done, then at 4,000 miles from the center where gravity is 1 G, you would no longer be on the surface.

The density idea comes in when you move closer to the center of the Earth than 4,000 miles. For the real Earth, if you were 2,000 miles from the center, you would be 2,000 miles under ground and gravity would be less because of all that mass above you pulling the other way and canceling some of the force. But if you compressed the Earth down to a size less than 2,000 miles, then you could be 2,000 miles from the center and not below the surface, in which case gravity would be 4 G, or 4 times stronger, because the DISTANCE from the center was half as much. That is how a black hole works, It has the same mass as a normal object, but all squeezed into such a small volume that you can get really close to the center without going underground and the gravity can get really strong at such short distances.

Answer 3

Think of it this way:

The mass density means the concentration of the mass. Two separate concentrations of mass will obviously produce a different field around the two them than if they were mashed together. This is because the source of the field is actually coming from two different places.

If you have a single concentration of mass, though, the gravity does not all radiate from the center of the mass-- think of each individual particle is its own source. Two equal masses with different density will have different volumes, and their numerous particles will be in different size arrays. Therefore, a tighter grouping of sources (particles) will result in a different field than a looser (less dense) grouping of sources.

Remember, a black hole has infinite gravity-- not because it has infinite mass (nothing does), but because it has no volume (it's a singularity) and thus has infinite mass density: mass density=mass/volume=(finite mass)/0.

I hope this clears it up your question for you.

Answer 4

The gravitational field of an object IS dependent on its mass.
Mass density of any object also called the specific density, usually shows such density as a ratio of how much it masses (or weighs) compared to water, which has a mass density of 1.
So gold would be 19.3:1 or 19.3 times as heavy as water (at 4C at which temp water is at its densest).
That means that water weighs 1 gram per cu cm
gold weighs 19.3 grams per cu cm.

Answer 5

Gravitational attraction is figured on mass, not density, so I don't know what you are talking about.

F(g) = G*m(1)*m(2) / r^2

Answer 6

it's both.for example,if you drop a ball the earths gravity pulls it to the ground,but at the same time,the balls gravity is pulling at the earth,it's just not enough to do anything.
if that makes any sense.

Answer 7

in order for questions to be answered properly they must be asked properly.