Applications

Many modern inventions today use the principle of Archimedes' without most of the population knowing it. Here are a few examples.


1. Hydrometer

- A hydrometer is an instrument that is used to measure the density of a liquid.

- A hydrometer consists of a glass tube attatched to a glass bulb. At the base of the glass bulb, is placed lead  shots. The purpose of these lead shots is to enable the hydrometer to be in a more vertically upright position. The function of the glass bulb is to increase the buoyancy of the hydrometer.

- The sensitivity of the hydrometer can be increased by using a glass tube with a smaller diameter.


2. Submarine

- A submarine has a large ballast tank, which is used to control its position and depth from the surface of the sea.

- When the ballast tanks are filled with water, the weight of the submarine becomes greater than the buoyant force acting on it. So the submarine dives into the sea.

- To enable the submarine to rise up, compressed air is used to expel the water from the ballast tanks so that the weight of the submarine becomes smaller.


3. Hot-Air Balloons

- The atmosphere is filled with air that exerts buoyant force on any object.

- A hot-air balloon rises and floats due to the buoyant force (when the surrounding air is greater than its weight). It descends when the balloon weight is more than the buoyant force. It becomes stationary when the weight is equal to the buoyant force.

- The weight of the hot-air balloon can be controlled by varying the quantity of hot air in the balloon.  


4. Ships

 

    
- A ship floats on the surface of the sea because the volume of water displaced by the ship is enough to have a weight equal to the weight of the ship.

- A ship is constucted in a way so that the shape is hollow, to make the overall density of the ship lesser than the sea water. Therefore, the buoyant force acting on the ship is large enough to support its weight.

- The density of sea water varies with location. The plimsoll line marked on the body of the ship acts as a guideline to ensure that the ship is loaded within the safety limit.

- A ship submerge lower in fresh water as fresh water density is lesser than sea water. Ships will float higher in cold water as cold water has a relatively higher density than warm water.