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					Archimedes’ Principle
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A relationship between buoyancy and displaced liquid was discovered by the Greek philosopher Archimedes. It states:

An immersed object is buoyed up by a force equal to the weight of the fluid it displaces.

Archimedes’ Principle
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2 key items to remember regarding Archimedes Principle: The weight of the water displaced (not the object) is equal to the buoyant force. The depth of the immersion does not matter; the displacement is the same at any depth.

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Archimedes’ Principle
Example # 1: A 1 liter bottle of Pepsi which has a mass of 2kg is immersed under water. What is the buoyant force on it?

Archimedes’ Principle
Example # 1: - The amount of water displaced is 1 liter due to the volume of the Pepsi. It’s mass has no impact at all. - 1 Liter weighs 10 N due to gravity. Buoyant force acting on Pepsi bottle = 10 N

Archimedes’ Principle
Example # 2 The 1 liter Pepsi bottle is thrown into a pool. As it sinks deeper and deeper, does the buoyant force increase, decrease, or remain the same?

Archimedes’ Principle
Example # 2 - Buoyant force acting on the Pepsi bottle will remain the same. The depth of the object makes no difference on displacement.

Archimedes’ Principle
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When objects are submerged in water, their weight will appear to decrease due to the buoyant force pushing on it.

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The difference between the weight of an object in air and its buoyant force will equal the object’s apparent weight while submerged under water.

Archimedes’ Principle
Example # 3: A brick has a weight of 3N in air. When submerged in water, it displaces 2 N of water. What is the brick’s apparent weight when submerged?

Archimedes’ Principle
Example # 3: - Because the brick displaces 2N of water, the buoyant force must also be 2N.

Weight in air – buoyant force = Apparent weight 3N – 2N = 1 N

Flotation
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How do large ships stay afloat while in the ocean? The answer relates to the shape of the hull of the ship and displacement of water.

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Flotation
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The shape of a ship’s hull is a curved bowl shape. The shape allows a greater volume of water to be displaced, and thus a greater buoyant force is exerted on the boat.

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Flotation
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The Principle of Flotation = a floating object displaces a weight of fluid equal to its own weight.


				
DOCUMENT INFO
Description: Describes what the Archimedes Principle is and how it relates to flotation.