Chapter-9 The Behavior of Fluids

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Chapter-9 The Behavior of Fluids
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Outline

• 1 Pressure, Hydraulics, and Pascals Principle
• 2 Atmospheric Pressure and the Behavior of Gases
• 3 Archimedes Principle
• 4 Fluids in Motion
• 5 Bernoullis Principle
• Everyday Phenomenon
• Throwing a Curve Ball

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A steel boat floats, but a piece of metal sinks.
Why?
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Fluids
Fluids are materials that can flow, gases and
liquids. Air is the most common gas, and moves
from place to place as wind. Water is the most
familiar liquid.
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Pressure
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Tire Pressure
People who have fixed a flat tire know something
about pressure.
In colliding with the inner walls of the tire,
the air molecules (blue dots) exert a force on
every part of the wall surface.
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Pressure
The pressure P exerted by a fluid is defined as
the magnitude F of the force acting perpendicular
to a surface divided by the area A over which the
force acts
The SI unit for pressure newton/meter2 (N/m2)
pascal (Pa).
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Area of a square
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Area of a rectangle
Width
Length
Area Length x Width.
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Area of a circle
d
Area ?r2, d diameter 2r.
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Pressure acts everywhere
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Pressure Acts Everywhere
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Pascal's Principle
Any change in the pressure applied to a
completely enclosed fluid is transmitted
undiminished to all parts of the fluid and the
enclosing walls.
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Hydraulic Jack
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Car Lift
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Hydraulic Car Lift
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E5
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Atmospheric Pressure
Atmospheric pressure at sea level is 1.013 105
Pa, which is sufficient to crumple a can if the
inside air is pumped out.
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Mercury Barometer
At sea level, Height of mercury h 76 cm.
Atmospheric pressure 76 cm of Hg. (76 cm 760
mm 29.9 inch)
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Variations in atmospheric pressure
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Density of air decreases as the altitude increases