 # Chapter 3 Section 2 Buoyancy and Density

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Chapter 3 Section 2 Buoyancy and Density

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?