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Density and Buoyancy
The definition of Density
the amount of matter in a given space, or volume
The equation for finding density
D=M/V or Density = Mass/Volume
common units for density
g/cm3 or g/mL or kg/m3 or kg/L
Density of water
Is density a physical or chemical property
definition of buoyant force
the upward force that fluids exert on all matter
the buoyant force on an object in fluid is an upward force equal to the weight of the fluid that the object takes the place of, or displaces
objects that float in water have a density
less than 1 g/mL
objects that sink in water have a density
greater than 1 g/mL
when an object's weight is greater than the buoyant force
the object will sink
when an object's weight is less than the buoyant force
the object will buoy up
when an object's weight is equal to the buoyant force
the object will float
Why do helium balloons float and balloons filled with carbon dioxide don't?
helium is less dense than air while carbon dioxide is more dense than air
How can a steel ship float when steel has a higher density than water?
the ship's hull is shaped so that the ship has a larger volume and therefore a smaller density
How do you make a submarine sink?
Fill the ballast tanks with water to increase the density of the submarine
How do you make a submarine rise?
Pump air into the ballast tanks to decrease the density of the submarine
Common units for liquid volume
mL or L
Common units for solid volume
cm3 or m3
Common units for mass
g or kg
how to find the volume of a cube
how to find the volume of an irregular solid
water displacement : H2O final vol - H20 initial vol
tool used to find mass
triple beam balance