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If an object have the density equal to water,what will happen when it is placed on the surface of water?
Buoyancy is the upward force exerted on an object immersed in a fluid. Of course, water is the most common fluid, but buoyancy also applies to hot air balloons (where the fluid is the surrounding air) and many other situations. What's the basic idea?

Archimedes figured out that the key to buoyancy is how much volume the object displaces compared to its weight. Archimedes Principle of buoyancy states that the upward force on an object in a fluid is equal to the weight of the fluid that is displaced. If this bouyant force is less than the weight of the object itself, the object will be left with a net downward force and will sink. If the object floats, it floats enough that the bouyant force exactly balances its weight.

For solid, uniform objects like an iceberg, this boils down to the object's mass density, its mass divided by its volume, usually represented by the Greek letter . For something like a boat hull, which is hollow, not uniform, you have to just look at the total weight and the volume of displaced water.


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