Density/Archimedes' Principle

Density

a measurement of how much matter is contained in a certain volume of a substance
(mass per unit volume of a substance)

Density Equations (and Variations)

D = m / V
m = D * V
V = m / D

Symbol for density, mass, and volume

D = density
m = mass
V = volume

Units

Volume = cm^3 or mL
Density = g/cm^3 (solid) or g/mL (liquid)

Density Demonstration 1

Pepsi vs Diet Pepsi
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regular pepsi sunk and diet floated (same with coke)

Reg. Water vs Salt Water
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carrots sinks in reg. water and floats in salt

Learned:
if you pack MORE MASS into the SAME VOLUME, it is MORE DENSE

Density Demonstration 2

sheet of paper vs paper football
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paper football more dense because smaller volume and same mass as sheet

Learned:
if you pack the SAME MASS into a SMALLER VOLUME, its MORE DENSE

Density Demonstration 3

Marble vs Golf Ball vs Bowling Ball
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marble and golf ball sank while the bowling ball floated (8lbs)

Learned:
Just because something has MORE MASS doesn't mean it is MORE DENSE

Buoyancy

ability of a fluid to exert an upward frce on an object placed in it (acts in the opposite direction of gravity )
-buoyant force on an object is equal to the weight of the fluid displaced by the object

Archimedes' Principle

the physical law that states that an object is pushed upward by a force equal to the weight of the fluid it displaces

Archimedes' Principle for Floating Object

the upward force is equal to the weight of the object; this implies that the mass of the displaced fluid is equal to the mass of the floating object

Archimedes' Principle for Sinking Object

the upward force is less than the weight of the object; this implies that the mass of displaced fluid is less than the mass of the sinking object (if it sinks though the volume is = volume of displaced water)