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Section 2 Properties of Fluids
What You’ll Learn
 Explain Archimedes’ Principle
 Explain Pascal’s Principle
 Explain Bernoulli’s principle and explain how we use it

https://www.brainpop.com/science/motionsforcesandtime/buoyancy/
How do ships float?
Buoyancy is the ability of a fluid (liquid or gas) to exert
an upward force on an object that is immersed in it.
Buoyant force = object’s weight  object floats
Buoyant force < object’s weight  object sinks
Archimedes’ Principle
 Who? 3rd century BC Greek
mathematician who made a
discovery about buoyancy
 Discovered? Found that the
buoyant force on an object is equal
to the weight of the fluid displaced
by the object
EXAMPLE
 Place wood block in water
 block will push water out
of the way as it begins to
sink until the weight of
the water displaced = the
block’s weight
 RESULT: buoyant force
= weight of the block
FLOATS
Would a steel block and wood block
that are both the same volume float?
Steel Block vs. Wood Block
Both displace same volume buoyant force is same
BUT steel sinks and wood floats- WHAT’S THE DEAL??
Density = mass / volume
Mass
Volume
Steel
24 g
8 cm3
Wood
4g
8 cm3
Density
Sink or
Float?
Pascal’s Principle
 Pressure- def. the force exerted per unit area
 Pressure (N/m2) = Force (N) / Area (m2)
 Who? Blaise Pascal (1623-1662) French scientist discovered the
useful property of fluids
 Principle? Pressure applied to a fluid is transmitted throughout
the fluid.
 Ex: Squeeze one end of a toothpaste tube, toothpaste
emerges from the other end. The pressure has been
transmitted through the fluid toothpaste.
 Ex: Hydraulic machines in auto repair shops Fig 15
Bernoulli’s Principle
 Who? Daniel Bernoulli (1700-1782)
Swiss scientist who studied the
properties of moving fluids such as
water and air
 Principle? As the velocity of fluid
increases, the pressure exerted by
the fluid decreases.
 Demo Bernoulli’s principle
 Ex: principle used when designing
aircraft wings and hose-end sprayer
(fig 17)
Fluid Flow
 Viscosity – def. the resistance to flow by a fluid
 Ex: cold syrup flows slow= high viscosity; heated
syrup flows faster= low viscosity
 Viscosity decreases as temperature increases
Homework
 Section Review pg 489 #1-7