June 18 - Department of Physics & Astronomy at the University of Utah

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Thursday 6/18
PHYS 2010
Nathalie Hoffmann
University of Utah
Gauge Pressure
• ๐‘ − ๐‘0 = ๐‘”๐‘Ž๐‘ข๐‘”๐‘’ ๐‘๐‘Ÿ๐‘’๐‘ ๐‘ ๐‘ข๐‘Ÿ๐‘’
• ๐‘0 is the absolute pressure
• Gauge pressure shows how much the pressure exceeds atmospheric
pressure/absolute pressure
Archimedes’ Principle
• The buoyant force on an object immersed in a fluid is equal to the
weight of the fluid that the object displaces.
Volume Flow Rate (Q)
• Equation of Continuity:
• ๐‘„1 = ๐‘„2 = ๐‘๐‘œ๐‘›๐‘ ๐‘ก๐‘Ž๐‘›๐‘ก
•๐‘„=
ΔV
Δt
• (flow rate gives the volume of fluid passing a certain point in a given time
interval)
• ๐‘„ = ๐ด๐‘ฃ
Steady vs. Unsteady Flow
• Steady flow: the flow pattern at any given point does not change with
time, at any given point the flow velocity remains constant with time;
does not mean the flow velocity is constant everywhere
• Unsteady flow: the flow velocity at a given point can change with
time
Laminar vs. Turbulent Flow
• Laminar flow: each bit of fluid follows a path called a streamline,
which do not cross
• Turbulent flow: no streamlines, adjacent bits of fluid can follow very
different paths
Viscosity
• Viscosity is an intrinsic resistance to flow. Because adjacent parts of a
fluid move at different velocities, the parts rub and exert frictional
forces on each other.
Bernoulli’s Principle
• In a moving fluid, the pressure is low where the fluid is moving rapidly
• ๐‘1 +
1
๐œŒ๐‘ฃ12
2
+ ๐œŒ๐‘”๐‘ฆ1 = ๐‘2 +
1
๐œŒ๐‘ฃ22
2
+ ๐œŒ๐‘”๐‘ฆ2
• Assumptions: steady, laminar flow
Bernoulli’s Principle
• In a moving fluid, the pressure is low where the fluid is moving rapidly
• ๐‘1 +
1
๐œŒ๐‘ฃ12
2
+ ๐œŒ๐‘”๐‘ฆ1 = ๐‘2 +
1
๐œŒ๐‘ฃ22
2
+ ๐œŒ๐‘”๐‘ฆ2
• Assumptions: steady, laminar flow
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