Density & Buoyancy Physical Characteristics of an Object

Characteristics A special quality or feature that someone or something has, and that makes that person or thing different from others Feature, quality, property, and attribute (all have similar meanings)

Volume The amount of space an object contains or a substance fills up Volume of a regular solid  V = l * w * h orE 1 * E 2 * E 3 Volume of an irregular solid  The measure of the displacement of liquid

Volume of Irregular Solids

Volume (Units) The unit for solid volume is cm 3 The unit for liquid volume is ml 1 cm 3 is equal to 1 ml

Volume (Units)

Mass The amount of stuff in an object The unit for mass is the gram (g) We measure mass on a scale

Density A measure of the amount of matter present in a given volume of a substance The measure of the amount of stuff in the space that an object takes up The more packed something is the greater its density

Density (Equation) Density = Mass/Volume The unit of density is g/cm 3 or g/ml

Pressure in Fluids A measure of how much force is acting on a certain area The unit of pressure is a pascal (Pa) and is equal to a N/m 2 A fluid is a liquid or a gas, not just a liquid

Pressure in Fluids Pressure in fluids happens in all directions Think about being in a pool The water surrounds you and pushes in on every side of you This is identical to being in air, the air pushes on every surface of your body

Pressure and Density Denser fluids have more mass, but how does that effect pressure This means that they have more stuff and therefore more pressure The denser the fluid, the more pressure it exerts

Pressure and Depth Pressure increase with depth in the fluid The deeper you are in the air or water, the greater the pressure This is because the weight of the column above you increases

Buoyant Force The upward force a fluid exerts on an object in the fluid This force is exerted on objects that sink and float When an object sinks, it is because its downward force is greater than the buoyant force

Buoyant Force Air or any other gas, is also a fluid and exerts a buoyant force The size of the buoyant force equals the weight of the displaced fluid

Archimedes’ Principle A Greek scientist discovered a connection between the amount of water displaced and the buoyant force He found that the buoyant force equals the weight of the displaced water

Buoyant Force & Density The strength of the buoyant force depends on the density of the fluid This is because the volume of the object would displace the same amount of fluid A denser fluid would weigh more

Floating and Sinking To determine if an object will float or sink you need to know two things: its weight and the buoyant force in the fluid you are going to place it in The greater force wins