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== Physical phenomenon == | == Physical phenomenon == | ||
When sea ice floats, it is subjected to two forces | |||
* Gravity, equal to the weight of the ice block (Figure 1) : | |||
* Archimedes' thrust, equal to the weight of the volume of water displaced by the ice block (Figure 2). | |||
* | |||
* Archimedes' thrust, equal to the weight of the volume of water displaced by the ice | |||
Since the ice cube is in equilibrium, the two forces compensate each other. The weight of the ice cube is therefore equal to the weight of the volume of water displaced. The same weight means the same amount of matter. Therefore, once melted, it will occupy exactly the volume that was below its waterline before it melted. It will therefore not contribute to raising the water level (Figure 3). | Since the ice cube is in equilibrium, the two forces compensate each other. The weight of the ice cube is therefore equal to the weight of the volume of water displaced. The same weight means the same amount of matter. Therefore, once melted, it will occupy exactly the volume that was below its waterline before it melted. It will therefore not contribute to raising the water level (Figure 3). | ||
This works for an ice cube, but it also works for an ice pack that is nothing more than a large ice cube. This demonstration only works if the ice is not supported by something solid. | This works for an ice cube, but it also works for an ice pack that is nothing more than a large ice cube. This demonstration only works if the ice is not supported by something solid. | ||
== Limits == | == Limits == |
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