This is an interesting video filmed in lake Saarijärvi in Vaala, Finland. If you didn’t figure it out by the end of the video, the divers are upside down. That’s why the air from their SCUBA masks is going down instead of up. They are held up against the bottom surface of the ice by their own buoyancy.
Buoyancy arises from the fact that fluid pressure increases with depth and from the fact that the increased pressure is exerted in all directions (Pascal’s principle) so that there is an unbalanced upward force on the bottom of a submerged object. Read More
Bouyancy explains why boats and balls, and swimmers float in water, it also explains why they sink. Boats made of heavy, dense steel float because they create a bubble of air that makes the displace more than their mass. The NOVA website has a great section on Bouyancy with explanations and experiment you can try.
When you place a block of wood in a pail of water, the block displaces some of the water, and the water level goes up. If you could weigh the water that the wood displaces, you would find that its weight equals the weight of the wood. Read More
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Source: PBS: Buoyancy Basics and Buoyancy Brain Teasers
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