F. Properties of Fluids

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F. Properties of Fluids 1. Archimedes
Principle a. Fluids exert an upward force on
objects. It is called the buoyant force.
b. The buoyant force is equal to the weight
of the fluid displaced.
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If the weight of the displaced fluid equals the
weight of the object, the object floats.
Fbuoy
Fw Fbuoy
Object floats
Fw
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If the weight of the displaced water is less than
the weight of the object, the object sinks.
Fw gt Fbuoy
Fbuoy
Object sinks
Fw
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How can a steel ship float?
The hull contains mostly air and displaces a lot
of water...enough so that Fbuoy Fw and it
floats.
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2. Pascals Principle a. Pressure is force
per unit area. P F / A
b. Pressure applied to a fluid is transmitted
throughout the fluid.
F1
F2
The Pascal (Pa) is the SI unit for pressure
A1
A2
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3. Bernoullis Principle a. As the velocity
of a fluid increases, the pressure exerted by the
fluid decreases.
lower pressure
oncoming air
lift
b. The curved upper surface of a wing causes
the air to flow over it faster and creates lower
pressure above the wing. This makes lift.
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4. The Venturi Effect a. Fluids flow faster
in narrower spaces and create lower air pressure
inbetween them.
b. Strong wind between buildings. c.
Big trucks passing small cars.
d. Landscapers use trees to channel and
create wind.
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5. Viscosity a. The resistance of a fluid
to flow.
b. Higher temperatures increase the movement of
fluid particles and make them flow easier (lowers
their viscosity).
An experiment to measure the viscosity of tar