C4.2 Buoyancy Physical Science

C4.2 Buoyancy Supplies: Pencil and Science Journal Standards: – 8c) buoyant force on an object in a fluid is an upward force equal to the weight of the fluid the object has displaced – 8d) students can predict whether and object will float or sink – 9f) Apply simple mathematical relationships to determine a missing quantity in a mathematical expression

C4.2 Buoyancy You will be taking notes using Cornell Notes format or Charting Notes format.

Warm Up 1.Find the density of an object if its mass is 143 g and its volume is 13.8 mL. 2.Calculate the mass of matter with a density of 1.2 g/cm 3 and a volume equal to 76 cm 3

C4.2 Buoyancy Definitions Weight: the downward force of gravity acting on a mass Buoyancy: the measurement of the upward force a fluid exerts on an object that is submerged. Archimedes’ Principle: states that the buoyant force is equal o the weight of the fluid displaced by an object.

Buoyancy Mass vs weight

Weight and buoyancy A force is a push or a pull Buoyant force is the upward push a fluid exerts on an object that is submerged. Buoyancy is the measure of a buoyant force

Your Own Words What is the difference between buoyant force and buoyancy?

Weight and buoyancy Depends on how much of the object is underwater As you push a beach ball down into the water, the buoyant force gets stronger

Imagine this You are in a swimming pool, with your hands on the edge at the deep end. What happens as you fill your lungs with air? What happens when you exhale the air? Write down your answer. Then compare the answer with your neighbor.

Archimedes’ Principle 3rd century, Greek mathematician Buoyant force is equal to the weight of the fluid displaced by an object

Sinking and floating If the buoyant force is greater than an objects weight, it floats. Positive buoyancy If the buoyant force is less than an objects weight, it sinks. Negative buoyancy. If the object stays where you place it in the fluid, Neutral buoyancy.

What floats List 3 things that float in a pool. List 3 things that sink to the bottom of a pool.

Density and buoyancy If you know an objects density, you know if it will sink or float. Water has a density of 1.00 g/cm 3 Consider average density

What is a Fluid Buoyancy doesn’t just apply to water. A fluid is a liquid or a gas. Heavier gases sink toward the ground

Why Why does a hot air balloon float? What makes it stop going up?