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## Chapter 3 Section 2 Buoyancy and Density

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**Density Review**• Density = mass(g) volume(cm3) • The density of water is 1 g/cm3 • A less dense object floats on a more dense object. • The same is true for liquids.**Density Practice**• A piece of wood has a mass of 10g and a volume of 20 cm3. Will it float in water? • A ball has a mass of 50g and a volume of 25 cm3. Will the ball float in water?**Buoyancy**• All liquids and gases exert a buoyant force on matter. • Gravity exerts a force downward. • The buoyant force exerts an upward force.**Floating**• In order to float the buoyant force must be greater than the force from gravity. • Gravity is a pulling force. • Buoyancy is a pushing force.**Archimedes’ Principle**• The buoyant force is equal to the weight of the fluid displaced by an object. • Example: A object displaces 50 N of water the buoyant force will be 50 N**Floating/Sinking**• If an object weighs 50N and displaces 50N of water, it will float. • If an object weighs 150N and displaces 100N of water, it will sink.**Practice**• An object has a mass of 250g and displaces 200g of water. Does it float? • An object has a mass of 50g and displaces 70g of water. Does it float?