What is the Law of Flotation?

The law of flotation states that when an object floats in a liquid, the weight of the liquid displaced by the submerged part of the object is equal to the total weight of the object. This means that for an object to float, it must displace an amount of liquid that weighs the same as the object itself.

Understanding the Law of Flotation

The concept might sound complex, but it's quite simple. Imagine placing a wooden block in water.

Key Points:

• Weight of the Object: This is the force of gravity acting on the object's mass.
• Displaced Liquid: When you put the block in water, it pushes some water out of the way. This is the displaced water.
• Weight of Displaced Liquid: This is the force of gravity acting on the mass of the water that was pushed aside.

How it Works

Here's how the law of flotation dictates whether an object floats:

• Floating: An object floats when the weight of the displaced liquid is equal to the weight of the object. In this case, the buoyant force (the upward force exerted by the liquid) is equal to the object's weight, and it suspends the object in the water.
• Sinking: An object sinks when the weight of the displaced liquid is less than the weight of the object. This means the buoyant force is insufficient to support the object’s weight.
• Submerged (Neutral Buoyancy): An object is submerged but not sinking when the weight of the displaced liquid is exactly equal to the weight of the object, but the object is fully under the water.

Practical Examples

Here are a few examples to solidify your understanding:

• Ship: A massive ship floats because its hull is designed to displace a huge volume of water. The weight of this displaced water is equal to the ship's weight.
• Log: A log of wood floats because it's less dense than water. This allows the log to displace its weight in a smaller volume than something of the same weight, but greater density.
• Steel Ball: A small steel ball sinks because it's very dense and doesn't displace enough water to equal its weight. If it was shaped into a boat, then it would displace a larger volume of water, and could potentially float.

Summary Table

In essence, the law of flotation is a fundamental principle that governs how and why objects float. It emphasizes the balance between the weight of an object and the weight of the liquid it displaces.