Floating & Floating & Sinking NotesSinking Notes

p. 52p. 52

I. BuoyancyI. Buoyancy

• Ability to floatAbility to float

• Archimedes’ principleArchimedes’ principle – – buoyant force = weight of fluid buoyant force = weight of fluid displaceddisplaced

A solid block of steel sinks when A solid block of steel sinks when placed in water. A steel ship with placed in water. A steel ship with the same weight floats.the same weight floats.

II. DensityII. Density

• Mass per unit volumeMass per unit volume

• ““How much stuff in a specific amount of How much stuff in a specific amount of space”space”

• Volume

MassDensity

1. Examples:1. Examples:

Volume

MassDensity

g/mL 105

50

mL

ga) Mass = 50 g, Volume = 5 mL

b) Mass = 100 g, Volume = 10 cm3

33

g/cm 1010

100

cm

g

2. Comparing Densities2. Comparing Densities

• Density of pure water = 1 g/mLDensity of pure water = 1 g/mL

• If an object is MORE dense, it will If an object is MORE dense, it will _____ _____

• If an object is LESS dense, If an object is LESS dense, it will it will __________

• If it has EQUAL density, __________If it has EQUAL density, __________

sink

float

suspends

Forces in Fluids - Floating and Sinking

Density

Changes in density cause a submarine to dive, rise, or float.

Comprehension CheckComprehension Check

1) Which has the greater 1) Which has the greater density?density?

a)a) CokeCoke

b)b) Diet CokeDiet Coke

c)c) They have the same densityThey have the same density

d)d) Not enough informationNot enough information

2) Assuming this is a tank of 2) Assuming this is a tank of pure water…pure water…What is the density of Coke?What is the density of Coke?

a)a) < 1 g/mL< 1 g/mL

b)b) > 1 g/mL> 1 g/mL

c)c) = 1 g/mL= 1 g/mL

d)d) Not enough informationNot enough information

3) Which block has the higher 3) Which block has the higher density?density?

a)a) Block 1Block 1

b)b) Block 2Block 2

c)c) They’re the sameThey’re the same

d)d) Not enough informationNot enough information

Block 1 Block 2

4) Calculate the density:4) Calculate the density:Mass = 10 g; Volume = 10 mLMass = 10 g; Volume = 10 mL

a)a) 1 g/mL1 g/mL

b)b) 10 g/mL10 g/mL

c)c) 100 g/mL100 g/mL

d)d) Not enough informationNot enough information

5) Identify the unknown 5) Identify the unknown substance if Mass = 20 g; substance if Mass = 20 g; Volume = 20 mLVolume = 20 mLa)a) GoldGold

b)b) AirAir

c)c) WaterWater

d)d) MethanolMethanol

6) What property determines 6) What property determines whether an object floats or whether an object floats or sinks?sinks?a)a) WeightWeight

b)b) DensityDensity

c)c) TemperatureTemperature

d)d) SpeedSpeed

ReferencesReferences

• http://www.pbs.org/wgbh/nova/lasalle/buoybasics.htmlhttp://www.pbs.org/wgbh/nova/lasalle/buoybasics.html

• http://www.nyu.edu/pages/mathmol/textbook/density.htmlhttp://www.nyu.edu/pages/mathmol/textbook/density.html