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Q & A: Neutral buoyancy

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Most recent answer: 10/22/2007
Q:
If the density of something is equal to the density of the water that it needs to be floated on, Will it sink or float ?
- Karthik (age 6)
VA
A:
In this case, we say it has the property of "neutral buoyancy". Your object will neither sink nor float, but will stay where you put it.

Of course nothing is perfectly, exactly equal, or if it is, it won't stay that way forever. If the temperature changes, the relative densities of your object and the surrouding water may change. Changes of even a tiny little bit will nudge the neutral buoyancy condition into something that just barely floats or just barely sinks.

Even water itself, which you might expect to have the same density as water which surrounds it, has enough density variations to cause convective currents. The ocean is full of water currents which are driven by temperature changes and changes in how much salt is dissolved, both of which affect the density of different bits of the water.

Tom

(published on 10/22/2007)

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