Application of Archimedes Principle
1. Ship
- a ship stays afloat by displacing the weight of sea water to its own weight.
- however, it may sink too deeply due to the overloading or changes in water density.
- as a prevention, a plimsoll line is marked on the hull of all ships to show the safe depth to be navigated
2. Submarine
- it has large ballast tanks to control its position and the depths it can submerge below sea level.
- when afloat, water is driven out from the ballast tanks by compressed air to reduce its weight and produce a larger buoyant force.
- when submerged, the ballast tanks are filled with water again to increase the weight of the submarine.
- it can submerge to a depth where the buoyant force is equal to its weight.
3. Hot-air Balloons
- it is used in :
a) weather forecasting b) sports c) recreation activities d) advertisements
- when the envelope of a balloon is filled with a gas of lower density than air such as hydrogen, helium or hot air, its weight decreases thus experiencing a buoyant force.
- if the buoyant force is equal to the total weight of the balloon, it remains stationary or continues to move upwards with constant velocity.
- if the buoyant force is greater than the total weight of the balloon, it would be accelerated upwards by a net upwards force.
4. Hydrometer
- an instrument for measuring densities of liquids.
- widely used in :
a) checking the condition of a car battery
b) testing the content of natural rubber in rubber latex
- consists of a wide bulb carrying a narrow glass stem.
- the lower bulb is weighted with lead shots to keep it floating upright.
- the immersed length of the hydrometer in a liquid decreases as the liquid density increases due to an increasing buoyant force.
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