| English | Principle of flotation |
|---|---|
| Bahasa Melayu | Prinsip keapungan |
| 中文 | 浮体原理 |
Definition
A floating object displaces a weight of fluid equal to its own weight.
In exam terms
The principle of flotation states that a floating object displaces a weight of fluid equal to its own weight. It is a special case of Archimedes' principle for an object that is in equilibrium while floating.
When an object floats, it is in equilibrium, so the upward buoyant force exactly balances its weight: F_buoyant = W_object. Because the buoyant force also equals the weight of fluid displaced, it follows that weight of fluid displaced = weight of the object.
Example sentence of correct use: A ship floats because it sinks just deep enough to displace a weight of water equal to the total weight of the ship and its cargo. This principle explains ships, hydrometers and the loading of boats.
Do not confuse it with Archimedes' principle
Do not confuse the principle of flotation with Archimedes' principle. Archimedes' principle applies to any immersed object, floating or sinking, and says the buoyant force equals the weight of fluid displaced.
The principle of flotation is the narrower statement that applies only when the object floats, adding that the displaced weight then equals the object's own weight.
In Paper 2 you may be asked to state the principle of flotation or to explain why a loaded ship sits lower in the water. A good answer links equilibrium (buoyant force equals weight) to the extra water displaced when more cargo is added.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)