Transcript Properties of Fluids

Buoyancy,
Density, and
Water
Properties of Fluids
Overview:
Archimedes’ Principle
Pascal’s Principle
Bernoulli’s Principle
Boyle’s Law
Density is the mass of a
substance per unit volume
(usually measured in grams
per milliliters, g/ml).
Buoyancy is the upward force
that a fluid exerts on an
object less dense than itself.
Q: How do ships float?
A: A greater force is pushing up on
the ship than the weight force
pushing down.
This supportive force is called buoyant force.
If the buoyant force is equal to the
object’s weight, it will float.
If the buoyant force is less than the
object’s weight, it will sink.
Bouyant force was explained
by Archimedes and it
became known as
Archimedes’ Principle.
Archimedes was a Greek
mathematician who lived
around the 3rd century
B.C.
Archimedes’ Principle
states that an objects
weight will cause the
object to sink while at
the same time
displacing the fluid.
If the weight of the
water displaced becomes
equal to weight of the
object, it floats.
If the weight of the
water displaced becomes
less than the weight of
the object, it sinks.
Q: Why is this
principle important?
A: Properties of fluids
ultimately determine
the design of ships,
airplanes, cars, and
hydraulic machines.
Water exerts pressure in all
direction.
Consider swimming in a pool.
The deeper you go the
more pressure you feel.
Pressure is a force exerted
on an object per unit area.
As you know pressure is
not exclusive to liquids.
The earth’s atmosphere
exerts pressure all
around you.
Pascal’s Principle
Pascal was a French
scientists who lived in the
1600’s. He discovered a
property of fluids now
known as Pascal’s Principle.
According to Pascal’s
Principle pressure applied
to a fluid is transmitted
throughout the fluid.
For example when you
squeeze a tube of
toothpaste at one end,
what happens?
Why?
Pressure is transmitted
throughout the fluid
toothpaste.
Calculating Forces Using Pascal’s
Principle
Pressure = Force/Area = F/A
In a system, P1 = P2::
F1 = F2
A1 A2
Pressure System
Bernoulli’s Principle
As the velocity of a fluid
increases, the pressure
exerted by the fluid
decreases.
Bernoulli’s Principle
Boyle’s Law
As a gas is squeezed into a
smaller space, its particles
will strike the walls more
often, increasing its
pressure.
The opposite is also true.
Calculating Pressure Using
Boyle’s Law
P1 V1 = P2 V2