why doesn't "the leaning tower of pisa" fall?
552897
As far as I know they spend many thousands of dollars each year on stablizing the foundations of the tower as well as the rest of the structure to ensure it doesnt topple over.
19024
I'm explaining this only on condition you don't try the experiment yourself.\n\nGiven that the Empire State Building is 1,250 feet tall and ignoring such factors as wind resistance for the moment, a penny dropped from the top would hit the ground in approximately 8.8 seconds, having reach a speed of roughly 280 feet per second.\n\nThis is not particularly fast. A low-powered .22 or .25 caliber handgun bullet, to which a penny is vaguely comparable in terms of mass, typically has a muzzle velocity of 800 to 1,100 FPS, with maybe 75 foot-pounds of energy.\n\nOn top of this we must consider that the penny would probably tumble while falling, and that the Empire State Building, like all tall buildings, is surrounded by strong updrafts. As a result the penny's descent would be substantially slowed.\n\nThus while you might conceivably inflict a fractured skull on some hapless New Yorker (or, more likely, some cretinous tourist from Towson), the penny would not "go through just like that." I bet it wouldn't even penetrate the skin. Not that I intend to find out.\n\nFor the record, the Empire State folks claim no one has ever dropped anything off their building. Yeah, right.\n-By Cecil Adams
225581
see if this helps.....\n\n\n\nAnalysis of a simple gravity pendulum\n \nFigure 2. Force diagram of a simple gravity pendulum.To begin, we shall make three assumptions about the simple pendulum\n\nThe rod/string/cable on which the bob is swinging is massless and always remains taut; \nThe bob is a point mass; \nMotion occurs in a 2 dimensional plane, i.e. pendulum does not swing in and out of the page. \nConsider Figure 2. The blue arrow is the gravitational force acting on the bob, violet arrows are that same force resolved into components parallel and perpendicular to the bob's instantaneous motion, the motion along the red axis, which is always perpendicular to the cable/rod. Newton's second law\n\n \nwhere F is the force acting on mass m, causing it to accelerate at a meters per second2. Because the bob is constrained to move on the green circular arc, there is no need to consider any force other than the one responsible for instantaneous acceleration parallel to the known path, the short violet arrow in our case\n\n \n \nLinear acceleration a along the red axis can be related to the change in angle θ by the arc length formula\n\n \n \n \nThis, however, is not the acceleration we seek because the gravitational force on the bob causes a decrease in angle θ. One accounts for that by placing a negative sign in front of a, thus:\n\n \n \n \nFigure 3. Trigonometry of a simple gravity pendulum.This is the differential equation which, when solved for θ(t), will yield the motion of the pendulum. It can also be obtained via the conservation of mechanical energy principle: any given object which fell a vertical distance h starting from rest, would have acquired kinetic energy equal to that which it lost to the fall. In other words, gravitational potential energy is converted into kinetic energy. Change in potential energy is given by\n\n \nchange in kinetic energy (body started from rest) is given by\n\n \nSince no energy is lost, those two must be equal\n\n \n \nUsing the arc length formula above, this equation can be re-written in favor of \n\n \nbut what is h? It is the vertical distance the pendulum fell. Consider Figure 3. If the pendulum starts its swing from some initial angle θ0, then y0, the vertical distance from the screw, is given by\n\n \nsimilarly, for y1, we have\n\n \nthen h is the difference of the two\n\n \nsubstituting this into the equation for  gives\n\n \nThis equation is known as the first integral of motion, it gives the velocity in terms of the location and includes an integration constant related to the initial displacement (θ0). We can differentiate, by applying the chain rule, with respect to time to get the acceleration\n\n \n \n \nsame as obtained through force analysis.\n\n[edit]\nSmall angle approximation\nThe problem with the equations developed in the previous section is that they are unintegrable. To shed some light on the behavior of the pendulum we shall make another approximation. Namely, we restrict the motion of the pendulum to a relatively small amplitude, that is, relatively small θ. How small? Small enough that the following approximation is true within some desirable tolerance\n\n \nif and only if\n\n \nSubstituting this approximation into (1) yields\n\n \nSolution to this equation is a well-known, and quite expected, oscillatory function\n\n \nwhere θ0 is the semi-amplitude of the oscillation, that is the maximum angle between the rod of the pendulum and the vertical.\n\nThe term  is a pulsation, which is equal to ,\n\nwhere T0 is the period of a complete oscillation (outward and return).\n\nSince ,\n\nthe period of a complete oscillation can be easily found, and we have obtained Huygens's law:\n\n \n \n[edit]\nArbitrary-amplitude period\nFor amplitudes beyond the small angle approximation, one can compute the exact period by inverting equation (2)\n\n \nand integrating over one complete cycle,\n\n \nor twice the half-cycle\n\n \nor 4 times the quarter-cycle\n\n \nwhich
113357
Yes...left it up in the air on the tower...hope it does return in the fall!
684710
A piece of iron has a density greater than water. Thus it will sink when the weight of the volume of water displaced by the piece of iron is less than the weight of the piece of iron. If iron is shaped, or used to make a ship,  the iron ship will float if the total volume of water displaced by the part of the ship in the water weighs more than the total weight of the iron used to make the iron ship. Thus, the upward force of buoyancy is greater than, or equal to,the downward force of gravity and the ship stays afloat.\n\nThis is called Archimedes's principle of buoyancy and it is fundamental to the design of all ships and heated air balloons.TWH
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.
675396
Cause a brick might fall on your feet.
845607
I'v heard about buildings being put on ball bearings so that the building will remain stable while the earth rocks beneith it. I'v seen a few specials on the Discovery Channel about it. Apparently the technology was pioneered in Japan. It makes sense since Japan has A LOT of earthquakes.
619968
The solidity of the ground. The ground was too soft to support the weigfht of the tower. The distribution of the towers weight on it's surface area required a more compact soil to be build upon. The engineers of that time didn`t have the means to predict this problem accuratly and hence the tower started leaning a fraction of an inch each year since the time it was built, untill it reached the weird inclination it has now.
675679
you'd fall very quickly and then go past the centre towards the surface at the other side.\nThen you'd start to fall back to the centre and go back to the other side.\nThis is basically how a pendulum works.\nBy the way.. there should be free fall at the centre of the earth... I.e. no gravity.
478202
If is really no wind, it should fall right back into your gun.\n\nBut an experimental proof I think can hardly be done because of friction effects between air and bullet: so you would need an evacuated tube of some 100 m height, higher than any building. And the accuracy of this tube also woud be hard to be realized.\n\nNevertheless, such an accuracy problem I think was encountered when was built the SLAC (STANFORD Linear Accelerator) in the 1950ies; but this installation was not upright.
361918
it won't sink, The Channel Tunnel ties the small island to main land and helps it float! =)\n\nhttp://en.wikipedia.org/wiki/Channel_Tunnel
699006
Because there is no atmosphere on the Moon, so no air resistance.  In the absence of air resistance, all objects fall down at the same rate.  Galileo is said to have shown that by dropping two weights from the top of the Tower of Pisa - they had different weights, but they landed at exactly the same time (so the story goes).  The only reason feathers usually take longer to fall is because of air resistance.
464783
The paper is out, because of wind resistance, leaving only the small and big rocks.  Refering to the 11th century-actually, Newton's law was supplanted some years ago, and we know that the acceleration due to gravity is determined by the combined gravitational forces of both objects.  Assuming an exactly equal shape and an exactly equal density of the two rocks, the larger would fall more rapidly, because of the involvement of it's own gravity.  If we assume, for example, that the small rock is the size of a baseball, and the big rock is the size of, oh...the moon, then the big rock will fall quite a bit faster (the combined gravity will be greater, because of greater mass).  As the large rock gets smaller, the gravity will decrease.  However, no matter how close in size the two rocks, there will be some difference.  It would not be easily measurable at anything less that a few million tons, but it would still be there.\nNewton was likely the greatest genius that ever lived...but we have moved beyond him in a lot of areas, including our understanding of gravity-
1044401
He will continue to fall.  This boils down to the idea of a net external force - in this case only gravity and drag play big roles.\n\nIf if pulls on his collar, his collar exerts an equal and opposite force on his hands.  His hands and arms transmit this force to the rest of his mass.  So...the net force he applies to his body is zero.
474729
That the coin is dropped directly on it's side, there is no wind, and both sides of the coin are perfectly equally weighted.\n\nHowever, due to chaos, just dropping the coin from any reasonable height will net an equal division over a large enough sampling of tests.
229934
according to engineering calculations , a wide area ceiling cant stand alone if its flat , then it needs colomns to support it , otherwise the dome shape is more stronger and can stand alone , only on its dia. needs support and no need in the middle , beside the beauty of its shape