Applying Archimedes's Principle

Archimedes's Principle.

(The Story of Archimedes' Palimpsest 2000)

Idea on Buoyant Force.

A less dense object floats in water.

1) The density of a object is less than that water since it contains air, thus is floats. 

2) Similarly, a large iron ship that has large space filled with air floats due to its lower density while a small solid iron sinks in water due to its higher density.

Idea of buoyant force.

3) For the object to float, its weight is balanced by the buoyant force (upthrust) acting upwards. If the buoyant force is larger than its weight, it bobs up to maintain the force equilibrium.

Applications of Archimedes' Principle in Everyday Life.

1) Ship

The ship

(a) The ship would sink to a certain level until its weight is equal to the buoyant force.

(b) To prevent this, a plimsoll line is marked on the hull of all ships to show the depths which are safe for them to navigate.

2) Submarine 

The submarine

(a) When afloat, water is driven out from the ballast tanks by compressed a larger buoyant force.

(b) The submarine can submerge to a depth where the buoyant to a depth where the buoyant force is equal to its weight.

3) Hot-air Balloons

(a) 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.

The total weight of the balloon = weight of the fabric + weight of the gas in the envelope.

(b) The balloon experiences a buoyant force = (volume of balloon) X (density of surrounding air) X g

The Hot-air balloons

(c) If the buoyant force is greater than the total weight of the balloon, it would be accelerated upwards by a net upwards force.

Hydrometer