1. SUBMARINE BOUYANCY How does submarines submerge and float.

2. OVERVIEW A submarine or a ship can float because the weight of water that it displaces is equal to the­ weight of the ship. This displacement of water creates an upward force called the buoyant force and acts opposite to gravity, which would pull the ship down. Unlike a ship, a submarine can control its buoyancy, thus allowing it to sink and surface at will.

3. TOPIC OUTLINE I. Introduction Submarine History II. Technology Parts and functions Process III. Advantages/Disadvantages of submarines IV. Videos/Images

4. SUBMARINE A submarine is a watercraft capable of independent operation underwater. It differs from a submersible, which has more limited underwater capability. The term most commonly refers to a large, crewed, autonomous vessel. It is also sometimes used historically or colloquially to refer to remotely operated vehicles and robots, as well as medium-sized or smaller vessels, such as the midget submarine and the wet sub. Used as an adjective in phrases such as submarine cable, "submarine" means "under the sea". The noun submarine evolved as a shortened form of submarine boat (and is often further shortened to sub). For reasons of naval tradition, submarines are usually referred to as "boats" rather than as "ships", regardless of their size

5. BRIEF HISTORY OF SUBMARINES 1580 The first published prescription for a submarine came from the pen of WILLIAM BOURNE. First submersibles The first submersible boat was built in 1620 by Cornelius Drebbel First military models The first military submarine was the Turtle (1775), a hand-powered acorn-shaped device designed by the American David Bushnell to accommodate a single person. In 1800, France built a human-powered submarine designed by American Robert Fulton, the Nautilus. In the American Civil War The Alligator was the first U.S. Navy submarine,designed by Brutus de Villeroi, first launched on May 1, 1862, TurtleThe 1862 Alligator,

6. Mechanically powered, late 19th century The first submarine not relying on human power for propulsion was the French Plongeur (Diver), launched in 1863, and using compressed air. In World War I Military submarines first made a significant impact in World War I. Forces such as the U-boats of Germany saw action in the First Battle of the Atlantic. In World War II During World War II, Germany used submarines to devastating effect in the Second Battle of the Atlantic. The French submarine Plongeur

7. SUBMARINE TECHNOLOGY: Submerging and floating

8. SUBMARINE TECHNOLOGY Whether a submarine is floating or submerging depends on the ship's buoyancy. Buoyancy is controlled by the ballast tanks, which are found between the submarine's inner and outer hulls. positive buoyancy. -- A submarine resting on the surface --means it is less dense than the water around it and will float --the ballast tanks are mainly full of air. negative buoyancy. -when the submarine submerge --Vents on top of the ballast tanks are opened. Seawater coming in through the flood ports forces air out the vents, and the submarine begins to sink. The submarine ballast tanks now filled with seawater is denser than the surrounding water. The exact depth can be controlled by adjusting the water to air ratio in the ballast tanks. neutral buoyancy. -That means the weight of the submarine equals the amount of water it displaces. The submarine will neither rise nor sink in this state. To make the submarine rise again, compressed air is simply blown into the tanks forcing the seawater out. The submarine gains positive buoyancy, becomes less dense than the water and rises.

9. MAIN PARTS AND FUNCTIONS Ballast Tanks Pressure hull

10. PARTS Ballast tank A ballast tank is a compartment within a boat, ship or other floating structure that holds water. In submarines ballast tanks are used to allow the vessel to submerge, water being taken in to alter the vessel's buoyancy and allow the submarine to dive. When the submarine surfaces, water is blown out from the tanks using compressed air, and the vessel becomes positively buoyant again, allowing it to rise to the surface. A submarine may have several types of ballast tank: the main ballast tanks, which are the main tanks used for diving and surfacing, and trimming tanks, which are used to adjust the submarine's attitude (its 'trim') both on the surface and when underwater.

11. PRESSURE HULL The pressure hull of submarines resists water pressure to make underwater transport possible. Pressure hulls make it possible to breathe in the extreme water pressure levels that are present in submarines. As a result, officers and crew on submarines can travel with comfort and ease. Pressure hulls are usually made of titanium or steel. The pressure hull is the inner hull of a submarine; this holds the difference between outside and inside pressure. Modern submarines are usually cigar-shaped. This design, already visible on very early submarines is called a "teardrop hull", and was patterned after the bodies of whales. It significantly reduces the hydrodynamic drag on the sub when submerged, but decreases the sea-keeping capabilities and increases the drag while surfaced.

12. BOUYANCY OF THE SUBMARINE

13. Submarines use buoyant forces and gravity to move up and down with in the water. When the Buoyant force is less than the Earth's gravitational pull on the submarine, it sinks, when the buoyant force is greater than the Earth's gravitational pull on the submarine, it rises. Once the submarine is already submerged, the buoyant force is constant. Submarines adjust the Earth's gravitational pull on it by filling the space in between the inner walls and outer walls with water and/or gasses. With out buoyant forces, the submarine would never return to the surface of the water.

14. ENVIRONMENTAL CONCERNS Ballast water Ballast water taken into a tank from one body of water and discharged in another body of water can introduce invasive species of aquatic life. The taking in of water from ballast tanks has been responsible for the introduction of species that cause environmental and economic damage. For example, zebra mussels in the Great Lakes of Canada and the United States. Sound pollution Noise pollution caused by shipping and other human enterprises has increased in recent history.The noise produced by ships can travel long distances, and marine species who may rely on sound for their orientation, communication, and feeding, can be harmed by this sound pollution. The Convention on the Conservation of Migratory Species has identified ocean noise as a potential threat to marine life.