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Density & Buoyancy
Transcript of Density & Buoyancy
What is Density?
Think about trying to lift a rock that is as big as a basketball. The rock and the basketball are the same size, so why is the rock heavier? The rock is heavier because it has more matter packed into the same volume of space.
Calculate the density of an object by dividing its mass by its volume.
Density = Mass/ Volume
So what does this have to do with me?
All matter has a physical property called density.
Density is the measurement of how much mass fits within a certain volume.
Density is measured in grams per cubic centimeter
Density describes how tightly the particles that make up matter are packed together.
An object will float if it is less dense than the gas or liquid in which it is placed.
It will sink if is denser than the gas or liquid in which is placed.
Can objects with the same volume have different densities?
Suppose you have two boxes of the same size: one filled with steel and the other with feathers. The box filled with steel would be denser. It would have much more mass in the same amount of space than the box filled with feathers.
What does density depend on?
You learned that matter is made of particles such as atoms or molecules. These particles have mass.
The density of a material depends on the masses of the particles that make up the material.
The more mass these particles have, the greater the density of the material.
The density of a material also depends on the distance between the particles in the material.
The particles of a solid tend to be packed tightly together. They don't have room to move around. However, the particles of a gas usually spread out.
Size and Density
The density of a substance is the same NO MATTER how much of the substance is present.
The density of an object depends only on the material the object is made from.
Each material has its own density.
What is buoyancy?
Liquids and gasses are fluids, which are materials that can flow.
When any object is submerged in a fluid, the fluid "pushes" in on the object.
The push is greater at the top, so the fluid pushes the object toward the surface.
Buoyancy describes the ability of an object to float in a liquid.
How can the amount of buoyant force be measured?
Ancient Greek philosopher Archimedes, the buoyant force on an object depends on the displaced fluid.
Archimedes' principle states that buoyant force is equal to the weight of the fluid that is displaced.