How does a hovercraft work?
149882
A craft is built on a solid platform, preferable strong but light weight.  The platform has a flexible skirt creating a border around the platform.  A very high powered fan forces air into the empty space between the platform and the ground, which is contained by the skirt.  As the flow rate of air increases, so does the pressure under the platform.  The pressure difference between the interior cavity and the top of the platform creates lift, just like an airplane wing.  As it lifts up, a gap forms between the ground and the skirt.  This reduces the pressure and lowers the lift.  The gap makes a self-regulating system.  As the gap shrinks, the pressure increases.  As the gap gets larger, the pressure decreases.  In this way the hover craft has a regulated height above air OR water.  Hovercraft over water can use higher power fans to elevate them so the craft won't impact waves as easily.  The air gap is higher, and the flexible skirts can interact with the waves and keep lift under the craft at all times.\n\nSimple hovercraft for the home builder can be made out of plywood, using a lawnmower engine for the lift fan, and another enging for the pushing fan.  Commercially available units can have one motor for both purposes and are a blast to drive.
538920
Hovercraft do rock. They are so much fun and you can barely even tell if you are on land or water. so cool.
461537
Before launch, the shuttle crew activates the the ship's rockets. At t=0, the Solid Rocket Boosters or SRBs are activated to provide the initial lift. As the name implies, the SRBs run on solid fuel in order to maximize thrust, but the design has a major drawback. Combustion of the solid fuel cannot be controlled in any way, and it will continue to burn the rest of the way until the fuel runs out 5 minutes later. So, the ship is stabilized before ignition.  After 5 minutes, the SRBs are jettisoned to lessen weight and the SRBs parachute back to earth. The shuttle continues on with the fuel in the external tank (the orange cone) attatched to its belly until the fuel it contains is used up 30 minutes later. That is then it is also jettisoned, but unlike the SRBs, the external tanks remain in space, for good. The shuttle then maneuvers itself around using its own fuel and thrusters to do the job it came up for. It may dock with the ISS, do some repairs, release its sattelite cargo or do whatever it came up to do.\n\nWhen it's time to head home, the shuttle again uses its thrusters and boosters to maneuver itself into low orbit and heads into the atmosphere for re-entry. As the shuttle heads deeper into Earth's atmosphere, friction between the shuttle and the air increases. The space shuttle is purposely built to utilize this effect for re-entry. Its design incorporates a flat base on the underside. That part and some others are generously covered with special ceramic tiles that can withstand temperatures up to 5000 degrees, depending on the thickness. So, the shuttle maximizes friction during re-entry by facing its underside to the direction it is travelling to, using the red-hot ceramic tiles to absorb the heat while slowing itself down. It is a dangerous procedure. If only one of the tiles cracked, went loose or dropped, the shuttle will disintegrate like shuttle Columbia. If the shuttle survives, it heads to its planned destination - a commercial runway. It slowly shifts its flying position back to aircraft-style and lands using landing gears and brake parachute.
112480
Hello, Every subamarine contains ballast tanks that when the needs to sink  it takes in water, due to the pressure and weight the submarine sinks and goes underwater and is propelled through propellars. When it needs to rise to suface, it lets the water out slowly and air comes and fills its ballest tanks and the submarine comes to surface. \n\nThats' it works, more info, check the web
583153
you need to slap who ever told you there are no stupid questions. This one is clearly stupid.\n\nWhy don't you ask how something in specific works.\nLike a motor, computer, nuclear reactor, water wheel, or something.
394450
there are different type of pumps but basically the pump is rotated by motor. fuel flows into the pump and by pump's rotation, its outflow will have higher velocity.
711381
Use the box of baking soda as a weight to provide torque to propel the vehicle and to wind the rubber bands. Once the box hits the ground, the hook can fall off and the rubber bands will unwind and propel the vehicle back the 1m.\n\nYou are using the box of baking soda as potential energy converted to kinetic energy to wind the bands and propel the vehicle.
160096
Water is carried as ballast (weight) this water is blown out of the boat with compressed air to raise the boat in the water. To sink the boat water is let in from the sea, which also helps to recompress the air. Emergency ballast in the form of metal attached to the bottom of the boat is sometimes carried to be released if there is a failure in the compressed air system. When the boat is on the surface, the compressed air is fully recharged by pumps.
1117618
when its ready it just has to go somewhere. It takes the path of least resistance trying to equalize its energy. It usually goes to ground.
686562
How does a ship float? Well, some ships are made of wood, and wood floats, so in that case is easy to understand. What about ships made of heavy steel, though? Or the concrete ships (above) that were constructed during a steel shortage at the end of WWI? Steel and concrete are heavier that water, how do they float? \n\nA ship will float as long as it weighs less than the water it pushes out of way, or displaces. Ships can use materials in their hulls that are heavier than water, but there must be air within the ship. Since the air doesn't weigh as much as the water, this lowers the weight of the ship compared to the same volume of water. Try this experiment to see how trapping air in a ship can make it float. You will need a lump of clay and a sink filled with water. \n\nSTEP 1 - Roll the clay into a ball and place it in the sink. Does it float? It shouldn't because the clay weighs more than the water. \n\nSTEP 2 - Now shape the clay into a rounded cup and put a small lump on the bottom as a keel. Put it in the water with the open part of the cup facing up so it stays filled with air. Does it sink? It shouldn't. As long as the bowl of the cup is large enough and contains air the clay will float. This is because the air makes the clay ship weigh less than the water it displaces. \n\nSTEP 3 - Now fill the bowl of the cup with water. Does it sink? It should. When the bowl is filled with water the clay ship weighs more than the water it displaces and sinks. \n\nWhen a ship floats it is said to have positive buoyancy. When it sinks it has negative buoyancy. \n\nFor another buoyancy experiment try the pencap submarine.
943048
Whenever the mass of an object is less than the mass of the liquid it displaces, it will float.  That's why a hunk of steel won't float, but a ship made of steel, enclosing lots of unoccupied space, will float.\n\nAs for the ice cream, its made up of lots of fat molecules whipped into a semi-solid.  Its mass is less than the mass of the root beer it displaces...therefore it floats
218971
Any object will float as long as it displaces a volume of liquid that is more massive than itself. Take the aluminum boat and fold it into a block of aluminum and it sinks. But due to the shape of the boat, the mass of the aluminum,plus you, and your fishing gear, is still less than the volume of water pushed aside by the hull of the boat. So, you float.
457731
I'd suggest a rocket but there are always going to be some people who say it's pushing against the air so you'll spend time explaining how a rocket really works. How about something that actually does push on the air, a fan-propelled car? Easy to make, easy to run (but not if you have to make quantitative measurements) Fan pushes air backwards, air pushes fan and car forwards.
304510
The same way it travels through air, in waves.  It just doesn't make it very far.
755704
How Does the Windmill Work?\n\nWind Energy\nWind is an indirect source of solar energy. It is caused by the uneven heating of the earth by the sun and the resulting redistribution of air to equalize energy in the atmosphere moving air from areas of high pressure to areas of lower pressure. The energy of the wind is transferred to the windmill’s sails where it is harnessed to perform work.\n\nThe cap of the windmill is turned with the winch attached to the bottom of the tail pole until the sails face the direction of the wind. Depending on the wind speed, wind boards are installed on the leading edge of the sails and canvas sail-cloths are unfurled across the sail-frames. The Miller climbs the sail-frame using the sail-bars like rungs of a ladder attaching the canvas to the cleats on the whip. High winds require less open sail than low wind. The Miller determines the amount of sail surface required based on wind speed and partially furls (reefs) the sails as required. The sails catch the wind and turn the wind-shaft.\n\nThe wind-shaft which is connected to the brake-wheel can be stopped with the brake which consists of a band of friction blocks encircling the brake-wheel attached to the brake lever and controlled via a rope near the tail pole attached to the brake lever. The turning brake-wheel turns the wallower connected to the upright shaft on the fifth level. A wood wheel on the fourth level is used to adjust any irregular spinning of the upright shaft.\n\nThe upright shaft is connected to a large gear called the spur-wheel on the third level. Power to run many things in the windmill is drawn from this wheel. Two stone-nuts turned by the spur-wheel drive quant shafts in turn rotating the runner stones; the top stones of the grinding stone pairs. The lower stone of the grinder is the bedstone; it remains stationary. The spur-wheel also turns a third lantern gear (trundle) to drive power transfer belts, pulleys and shafts used to operate the grain elevators, sifters, grain separator, corn sheller and a vacuum system.\n\nHow is Grain Ground into Flour?\nGrain and flour move through the system using grain elevators and gravity. Grain is carried into the windmill and poured into first level hoppers. From there it is cleaned in the basement with the corn sheller and grain separator. Grain elevators carry cleaned grain to the third level hoppers which hold it until it is dropped into the second level grinders. Corn & oats are ground in the west grinder and dropped into a ceiling mounted sifter on the first level. Wheat & rye are ground in the east grinder. The flour drops into an elevator at the ceiling of the first level, is carried back up to a hopper on the third level and dropped into the sifter on the second level. The sifted flour is stored in hoppers suspended from the ceiling on the first level.\n\nInteresting Notes\nThe windmill contains two scales; a floor scale in the windmill and a wagon scale outside the north end of the windmill. The scale inside the windmill can weigh individual bags of grain. The scale outside is used for weighing loaded and unloaded wagons.
408700
The following link is a pdf slide show that gives examples of buoyancy calculations and theory of floating objects.\n\nhttp://www.colorado.edu/physics/phys1010/phys1010_fa05/lectures/class12-09-29.pdf
258972
A ballast tank is tank used to hold ballast.  Ballast is weight used to steady or hold something down.  \n\nSubmarines rise and fall by altering their buoyancy (ability to float).  Archimedes principle states that the buoyant force is equal to the weight of water displaced by the object.  If the object weighs more than the amount of water it displaces, it will sink.  If it weighs less than the amount of water it displaces it will float. A submarine therefore alters is weight in order to alter its bouyancy.  A submarine submerges by allowing water to enter the ballast tank thus creating a negative buoyancy.  A submarine rises by blowing the water back out of the ballast tank thus producing positive buoyancy.