1. Presentation 1
Fluids and fluid statics

2. The three basic states of matter are solid, liquid
and gas while Plasma and Bose Einstein
Condensate are rarely observed in daily life.
States of matter

3. A fluid is anything that would spill or float away if it
weren't in a container (unless it's big enough to be
held together by gravity like a star). If you can stir it
up with a spoon or blow it through a straw, it's a fluid.
Water is a fluid and so is air. In fact, all liquids and
gases are fluids.
It is defined as a substance that continually deforms
(flows) under an applied shear stress.
Shear stress-The component of stress that causes
parallel layers of a material to move relative to each
other in their own planes.
Fluids

4. Compressibility – refers to whether its volume can
easily be increased or decreased.
Gases are highly compressible while liquids are
incompressible.
Density- the amount of matter in a given space for
that substance.
It is possessed by all fluids.
Pressure- the force exerted over a given area.
In a liquid, the pressure comes from the weight of the
fluid and the weight of the air above it, which we call
the atmosphere and the same principle applies to
gases.
Properties of Fluids

5. Buoyancy- the ability or tendency to float in a substance
Buoyancy is another common characteristic of fluids.This is
the upward force from a fluid, which is usually felt by some
object in that fluid. It comes from the pressure inside the fluid
itself.
Viscosity- the property of a liquid that describes how fast or
slowly it will flow.
Real fluids display viscosity and thus are capable of being
subjected to low levels of shear stress.

6. Viscosity of liquids in general, decreases with
increasing temperature while that of gases increases.
Surface Tension- the elastic tendency of liquids that
makes them acquire the least surface area possible.
It is an important property of fluid which enables
phenomenon like capillary action.
Rise or fall of a liquid in a capillary tube is caused by
surface tension and depends on the relative
magnitude of cohesion of the liquid and the adhesion
of the liquid to the walls of the containing vessel.

7. Fluid Statics and Fluid Dynamics form the two constituents of Fluid
Mechanics. Fluid Statics deals with fluids at rest while Fluid
Dynamics studies fluids in motion.
A fluid at rest has no shear stress. Consequently, any force
developed is only due to normal stresses i.e., pressure. Such a
condition is termed the hydrostatic condition.
Its importance becomes apparent when we note that the
atmosphere around us can be considered to be at rest and so are
the oceans. The simple theory developed here finds its application
in determining pressures at different levels of atmosphere and in
many pressure-measuring devices. Further, the theory is employed
to calculate force on submerged objects such as ships, parts of ships
and submarines. The other application of the theory is in the
calculation of forces on dams and other hydraulic systems.
Fluid Statics

8. Pascal’s law
The basic property of a static fluid is pressure. Pressure is
familiar as a surface force exerted by a fluid against the walls
of its container. Pressure also exists at every point within a
volume of fluid. For a static fluid, pressure at a point is same in
all directions.This is Pascal's law.
Px=Py=Ps=P

9. The formula that gives the pressure P on an object
submerged in a fluid is
P=h*ρ*g
Where ρ is the density of the fluid,
g is the acceleration of gravity
h is the height of the fluid above the object

10. Measurement of Pressure
One of the direct applications of the equation of Fluid Statics
we have derived is in the devices used to measure pressure.
Now it is necessary to recall that we have an Absolute
Pressure and a Gauge Pressure. Absolute pressure is the sum
of atmospheric pressure and the gauge pressure.

11. Barometers
A barometer is a device for measuring atmospheric pressure. A
simple barometer consists of a tube inserted in an open container of
mercury with a closed and evacuated end at the top and open tube
end at the bottom and with mercury extending from the container up
into the tube. Strictly, the space above the liquid cannot be a true
vacuum. The atmospheric pressure is calculated from the relation
Patm = ρgh where ρ is the density of fluid in the barometer.

12. Piezometer
For measuring pressure inside a vessel or pipe in which
liquid is there, a tube may be attached to the walls of the
container (or pipe) in which the liquid resides so liquid can
rise in the tube. By determining the height to which liquid
rises and using the relation P1 = ρgh, gauge pressure of the
liquid can be determined. Such a device is known as
piezometer.

13. The “U”-Tube Manometer
Using a “U”-Tube enables the pressure of both liquids and
gases to be measured with the same instrument.The “U”
is connected as in the figure below and filled with a fluid
called the manometric fluid.The fluid whose pressure is
being measured should have a mass density less than that
of the manometric fluid and the two fluids should not be
able to mix readily - that is, they must be immiscible.

14. Archimedes' principle
Archimedes' principle indicates that the upward
buoyant force that is exerted on a body immersed in
a fluid, whether fully or partially submerged, is equal
to the weight of the fluid that the body displaces.

15. Variation Of PressureVertically In A Fluid
Under Gravity
p2-p1= -ρg(z2-z1)
Thus in a fluid under gravity, pressure decreases with increase
in height, (z2-z1)

16. Equality of pressure at the same level in a static
fluid:
The fluid is at equilibrium so the sum of the forces acting
in the x direction is zero.
P1=P2

17. General Equation ForVariation Of Pressure In
A Static Fluid
dp/dz=-ρg
This equation predicts a pressure decrease in the
vertically upwards direction at a rate proportional to
the local density.