why does islands and contients float, but a rock doesn't?
819648
I believe that you are speaking of plate tectonics when referring to continents floating (islands do not...they are volcanic formations from oceanic plates), here is some info:\n\nContinents are made up of solid rock, and float in the fluid (a very viscous fluid) of the Earth's mantle (also called the magnasphere). If the specific gravity of the mantle and the specific gravity of continental material are known, it should be possible to calculate how continents float in the Earth's mantle. \nThe average continent is made up primarily of limestone, granite, or eroded granitic byproducts such as shale, siltstone, and sandstone, as well as metamorphics like slate, schist, and gneiss. However, most continents also have substantial amounts of andesite and basalt added in, from a past history of various volcanic events. The addition of these denser materials raises the average specific gravity for continental material to around 2.7. SiMa (from Silicon/Magnesium - its principal elements) is the material of the Earth's mantle - the 'fluid' in which continents are floating. To all appearances, this material is solid rock, but under the extreme pressure and temperature to which it is subjected, it actually flows like a liquid, albeit very slowly. Its specific gravity of 3.3 is high enough to insure that continents cannot sink. \n\nSo...it is all a matter of density...oceanic plates are made up of denser stone and so settle into the magnasphere lower than the lighter density continental formations.  As for the rock floating, I assume that you mean in water and the answer is the same...the density of the rock is much greater than water's...so it sinks.
12398
The rotational energy you impart to the object when spinning overcomes the force of gravity that would topple a stationary object.  \n\nA total layman's explanation:\n\nA perfect stationary top perfectly balanced will not fall over.  In real life though,it's impossible to perfectly balance a top.  It's shape practically guarantees that its center of gravity will not be directly over the balance point for any practical length of time.  Imperfections in the material will cause a slightly uneven weight distribution, air currents will introduce a small force, and mechanical vibrations will be transmitted through the medium the top rests on.  The upshot of all this is that as soon as the center of mass is no longer over the resting point, gravity is going to pull the top over.  \n\nNow gravity has an acceleration of 32 feet per second squared (if I remember my ancient high school course correctly).  It can only topple the top at a specific speed.  If you spin the top fast enough, any side that gravity tries to "pull down" will translate around so quickly that it literally has no time to fall.  If you were standing on a planet with a much higher gravity, you'd have to spin the top far faster to achieve stability, and if you were on the moon, it would spin for a much longer time. Eventually, however, the top starts to slow and the tip will inscribe little circles.  That action is called "precession".  And of course, eventually the thing drops to the table and the game is all up once it slows enough.\n\nAgain, that's a layman's view of how it works.  Some college physics major is probably going to come in here and make my answer look really foolish.
1140754
If you are refering to those real small islands at the north end, they are off limits because they go under water at high tide.  There is nothing on them for you to see because of this.
1063756
I think its not that earth is bearing any weight.When you put something like a block on the earth,earth exerts a force on the block.BUT the block also exerts the SAME force on the earth.So \nthe earth and the block are attracting each other,or are pulling each other with the same force.Therefore, no matter how much wieght you put on the earth,that thing will also attract the earth with same force.(So Earth wont ever fall!).I hope this helps.
373975
The Earth is not a perfect sphere so you are at different distances from the centre at different places.\nThe density of the Earth is not constant so above dense rocks you appear slightly heavier.\nThe Earth spins so at the equator you are lifted slightly by the Eotovos effect.
187526
It depends on how much water is displaced by the stone and log. The stone and log will be buoyed up by a force equal to the weight of the water displaced.
1047922
It all depends on buoyancy and density. \n\nIf the weight of an object is less than the weight of the fluid the object would displace if it was fully submerged, then the object is less dense than the fluid and it floats at a level so it displaces the same weight of fluid as the weight of the object.\n\nIf the object has exactly the same density as the liquid, then it will stay still, neither sinking nor floating upwards, just as the liquid nearby stays still.\n\nUNLESS, \n\nAn object made of a material of higher density than the fluid, for example a metal object in water, can still float if it has a suitable shape (ex: hollow) that keeps a large enough volume of air below the surface level of the fluid. In that case, for the average density mentioned above, the air is included also, which may reduce this density to less than that of the fluid.
39301
Think of it this way:  If an object weighs more than it would if it was made of water, it will sink.  If an object weighs less that it would if it was made of water it will float.\n\nA coin is made of solid metal which makes it denser than water, therefore heavier.  It will sink.  A ship is made of metal also, but NOT solid metal.  It also consists of other materials but mainly air (inside the ship).  This means it's lighter than water, which is why it will float.
1119337
The geological makeup of the Earth to begin with! It isnt a perfectly balanced orb. Secondly, the orbit of the moon and any other objects in the solar system with enough mass. Get your toy top out. A top is  not a perfectly balanced object. It would be impossible to attain this. Spin the top and watch its balance decay. Same principle.
289385
Denser materials can "float" in the sense of remaining suspended, if they are small enough; think of candle soot. The particles must be small enough so that their fall rate is dominated by their air resistance rather than their weight. Such floating is also helped by brownian motion.
897876
No piece of land is going up into space.. Im pretty sure a chunk of land isnt going to float up into space on its own
1142972
In short, ice float in water because it is less dense.\n\nDensity = mass / volume\n\nFor a more thorough explanation, one needs to look at what happens when liquid water freezes into solid water (ice).\nAs the water freezes and becomes a solid, it expands.  The volume of a given mass of water becomes larger, therefore the density decreases.  Without going into the effects of buoyancy to explain "why" less dense things float (the weight of the fluid they displace is greater than the weight of the object), just accept that they do.\n\nTo be even more thorough,\nWater expands when it freezes because of the strong, "Hydrogen bonding", intermolecular forces which exist between the water molecules in the liquid/solid.\nWhen water is a liquid, the molecules have much more freedom to move around and rotate any way they please, but when the water freezes into a solid, the molecules have significantly less energy (thus less freedom to move around) and try to take on the most stable/low energy state they can...which happens to be in a lattice structure which has a higher volume that when the molecules were in the liquid state.  So it is because of the Hydrogen bonding present between the water molecules that solid ice float in liquid water.
64876
Buoyancy is simple.  If the weight of the liquid moved by insertion of an object into the liquid is greater than the weight of the object, it will float.  That is why the size of ships are measured in displacement.  The "Displacement" refers to the weight of water that is "moved out of the way".\n\nThink of it this way - take two identical spheres with the exact same outer material and thinkness.  One is hallow, and one is filled with lead.  Of course, we know that the one filled with lead will sink?  Why?  Because it weighs more than the water that is being moved out of the way.  How do you make it neutrally bouyant?  Simply fill it with enough lead that equals the weight of the water displaced by the sphere.\n\nThis is called Archimedes Law of Bouyancy.  Google/Yahoo search it and you should find some illustrations to help explain.
918781
Where is your freebody diagram? There are other forces acting on the block than just gravity...\n\nGood Luck
157120
This goes along with the question of why don't we fall off the earth if it is round. The answer is because gravity is holding us (and the water) down.
171753
oldhippypaul is right, the correct statement is "both corks are subject to the same buoyant force". The explanation is that, if they´re identical,they weigh the same. Since there in balance (i.e., there not sinking or emerging) the bouyant force must equal thre weight and, therefore is fhe same.
914644
Any rock will sink if its density is greater than the liquid you are putting it in to. Likewise, it will float if its density is less than that of the liquid.\n\nSo, lava will usually float because it is filled with bubbles of air which makes the whole rock less dense than water. If you crush a piece of lava, the pices will probably sink.