Buoyancy and Archimedes' Principle
Why do some objects float while others sink? It's all about the buoyant force - the upward push that fluids give to objects. This happens because pressure increases with depth, creating more force on the bottom of an object than the top.
Archimedes' Principle gives us the secret: the buoyant force equals the weight of the fluid that gets displaced (pushed out of the way). The formula is FB = ρgVdisplaced, where you use the fluid's density, not the object's density.
Here's how it works in real life: if the buoyant force is stronger than the object's weight, it floats (positive buoyancy). If the object weighs more, it sinks (negative buoyancy). When they're equal, the object hovers (neutral buoyancy) - like a submarine underwater!
Remember: A floating object displaces exactly enough fluid to equal its own weight - that's why ice cubes don't overflow your drink!