# Float Your Boat

## BUOYANCY

Buoyancy is an upward force on any object immersed in a fluid. The formula for buoyancy can be defined as:

The pressure acting on an object in a fluid is equal to:

Thus,

depth * area = volume displaced

**F**

**igure:**Free body diagram of a barrel floating in water.

## ARCHIMEDES' PRINCIPLE

The buoyant force that is exerted on an object is equal to the weight of the fluid that the object displaces.

**Figure:** This illustrates Archimedes' Principle of buoyancy. As you can see, the 5kg mass displaces 2kg of water when immersed. The buoyant (upward) force acting on the mass is 2 kg. This reduces the mass's apparent weight by 2 kg - that is, from 5 kg to 3kg as shown.

## SINK OR FLOAT

An object's ability to float depends on its density relative to the density of the fluid.

**Figure: **This series of images compare the buoyancy of three barrels with constant volume but varying mass.

**Figure: **This series of images compare the buoyancy of three barrels with constant mass but varying volume.