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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