The buoyancy increases with the depth

Prisma Physik 2, textbook

Mysterious powers you have certainly already noticed in the swimming pool that you feel much “lighter” in the water ( b1). You can measure the forces that act on a body in the air and in water ( b3). to do this you attach a body, e.g. b. place a stone on a dynamometer and note the weight displayed. If you now completely submerge this stone in the water, the dynamometer shows less. there is therefore a force acting on the stone in the water which is directed against the force of weight. this force is called the buoyancy force F A. A buoyancy force F A acts on every body in the water. it is always directed upwards. Amazing now take a small lead cube that has the same mass as the stone. its volume is much smaller than the volume of the stone. If you submerge this cube in the water, you will find that the buoyancy force is less. So the buoyancy force does not depend on the weight, but on the volume of the submerged body. this was discovered by the naturalist A rChimedes (287–212 BC). Archimedes experimented A rChimedes found that the buoyancy force is as great as the weight of the water that a body displaces when it is immersed in a vessel. this discovery is called Archimedes law. the buoyancy force that acts on a body in the water is just as great as the weight of the fluid displaced by the body. Sinking - floating - climbing - swimming When a body is completely immersed in water, there are always two forces acting: the weight F G of the body acts downwards and the buoyancy F A upwards. if the downward weight force is greater, the body sinks. if both forces are equal, the body always floats at the same depth. on the other hand, if the upward buoyancy force is greater, the body rises. it emerges from the water until it protrudes so far that the buoyancy force is just as great as the weight. the body swims ( b2). Buoyancy and density Whether a cube sinks, floats, rises or swims in water can also be determined by its density. Cubes made of materials with a density greater than that of water sink. If the density of the material is the same as the density of water, the cube floats, if it is smaller, it rises. But why do iron ships swim when the density of iron is almost eight times that of water? the hull is not made entirely of iron, but contains cavities filled with air. this makes the volume very large and the mean density of the ship smaller than the density of the water. Task  look up the densities of lead, wood and oil. Indicate which of these substances sinks, floats, rises or floats in water. 2 when a ship goes from the sea (salt water) into a river (fresh water) - does it go more or less deeply? (Note: look at experiment 1!) Experiment   a) Put an egg in a beaker filled with water. how does the egg behave? Now add salt in portions to the water and stir well each time. can you add enough salt to make the egg float? b) what happens if you keep adding salt to the water? Describe your observation and try to explain it. F G F G F a 3 the buoyancy force F a acts upwards against the weight force F G.  this is where uplifting forces act 2 sink, float, rise and swim The buoyancy Go ahead Test purposes - property of the publisher öbv

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