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Chapter-9 The Behavior of Fluids


The Behavior of Fluids
1 Pressure, Hydraulics, and Pascal’s Principle
2 Atmospheric Pressure and the Behavior of
3 Archimedes’ Principle
4 Fluids in Motion
5 Bernoulli’s Principle
 Everyday Phenomenon:
            Throwing a Curve Ball
Variables That Are Commonly
   Used to Quantify a Gas

        Name                  Symbol

  Pressure                      P

  Volume                        V

  Temperature                   T

  Amount of gas,                n
  # of moles
                    Boyle’s Law
How does the volume of a gas change with pressure?
In order to observe this, we will visit the following Java site.
                    Boyle’s Law
How does the volume of a gas change with pressure?
In order to observe this, we will visit the following Java site.

Boyle’s law can be expressed using symbols as follows:

                P V  cons tan t

                   P1V1  P2V 2
 9.3archimedes’ Principle
 Archimedes of Syracuse

Much of Archimedes fame comes from his relationship with Hiero,
the king of Syracuse, and Gelon, Hiero's son.
At one time, the king ordered a gold crown and gave the goldsmith
the exact amount of gold to make it.
When Hiero received it, the crown had the correct weight but the
monarch suspected that some silver had been used instead of the
Since he could not prove it, he brought the problem to Archimedes.
One day while considering the question, "the wise one"
entered his bathtub and recognized that the amount of water
that overflowed the tub was proportional the amount of his
body that was submerged.
This observation is now known as Archimedes' Principle and
gave him the means to solve the problem.
He was so excited that he ran naked through the streets of
Syracuse shouting "Eureka! eureka!" (I have found it!). The
fraudulent goldsmith was brought to justice.
Buoyant Force
         Archimedes’ Principle

The buoyant force acting on an object fully or partially
submerged in a fluid is equal to the weight of the fluid
displaced by the object.

A measure of the frictional forces between the layers of a fluid
producing resistance to flow. Highly viscous fluids flow slowly.
The velocity increases rapidly from the wall inward for a low-
 viscosity fluid but more gradually for a high-viscosity fluid
Laminar and Turbulent flow
          9.5 Bernoulli’s Principle

For steady flow, the speed, pressure, and elevation of an
incompressible and nonviscous fluid are related by an
equation discovered by Daniel Bernoulli (1700–1782).
At the same elevation, the sum of the pressure plus the
kinetic energy per unit volume of a flowing fluid must
remain constant.

              1 2
           P  dv  cons tan t.
The pressure of a moving fluid is greater
   when the fluid velocity is smaller.
Demonstrating Bernoulli’s Principle
Lift on an airplane wing
A batter is fooled by a curveball
Spinning Baseball
Curveball Pitch

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