BUOYANT FORCE What makes objects float? Why do some objects float and others sink?

Floating & Sinking: • It’s not just weight! • It’s not just density! • Depends on 2 Forces: – Weight of an object GRAVITY – BUOYANT FORCE For example, aircraft carriers are 80 – 900 tons! Yet, they float. For example, much of an aircraft carrier is steel which has a density ~7.9 g/ml.

More About Fluids: Floating Science For solid objects to float, there must be something holding them up. We know that gravity is pulling down on the object But what is holding it up? Gravity

As a object sits in a fluid, the particles in the fluid push back on the object This “pushing back” is called a buoyancy force buoyancy force Gravity

How strong the buoyancy force is depends on the following: The shape and density of the solid The density of the fluid

What is displacement? • An object in water, will force water out of the way. • Moving water out of the way is called displacement.

(Think about changing volume!) Buoyant Force: Displacing water creates a force called buoyant force. Buoyant force = upward push created by displaced water Size of buoyant force = weight of water moved So, changing the amount of water displaced, changes the buoyant force. (Think about changing volume!)

Creating floating objects with materials denser than water: Buoyancy: Creating floating objects with materials denser than water: Change the VOLUME! Change the MASS.

Archimedes Principle Archimedes stated that You can figure out the Hello Stevie Do you like floating? Archimedes Principle Archimedes stated that You can figure out the Buoyancy force on an object simply by: Measuring the WEIGHT of the fluid it displaces Let’s do it!!!!