This document discusses several fluid properties including capillarity, density, surface tension, and viscosity. It defines capillarity as the ability of a liquid to flow in narrow spaces against forces like gravity. Capillarity can occur through rise or fall and is responsible for phenomena like water moving up plants and oil rising in wicks. Surface tension is caused by stronger attractive forces between liquid molecules than between liquids and gases, creating inward pressure on the surface. Viscosity is a fluid's resistance to flow, defined by Newton's law of viscosity as proportional to the velocity gradient. It describes the drag force on objects moving through fluids.

1. Name :- Margeel Shah -140410109094
Smarth Shah-140410109095
Smit Shah-140410109096
Rehan Shaikh-140410109097
Subject:-ATHE
Topic :-Fluid Properties Density , Viscosity ,
Surface tension & Capillarity

2. Capillarity

3. DEFINITION….
 Ability of a liquid to flow in narrow spaces without the
assistance of, and in opposition to, external forces like gravity
 Capillary action is sometimes called capillarity, capillary
motion, or wicking

4. EXAMPLES….
 Drawing up of liquids between the hairs of a paint-brush
 Drainage of constantly produced tear fluid from the eye
 Observed in thin layer chromatography
 draws ink to the tips of fountain pen nibs
 moving groundwater from wet areas of the soil to dry areas

5. TYPES…..
 Capillarities are of two types
 Capillarity rise
 Capillarity fall

6. CAPILLARITY RISE
 Tendency of liquids to rise in tubes of small diameter in
opposition to, external forces like gravity

7. CAPILLARITY FALL
 Tendency of liquids to be depressed in tubes of small
diameter in opposition to, external forces like gravity

8. APPLICATIONS…
 Lubricating oil spread easily on all parts because of their low
surface tension.
 Cotton dresses are preferred in summer because cotton dresses
have fine pores which act as capillaries for sweat.
 Dirt get removed when detergents are added while washing
clothes because surface tension of water is reduced.

9.  The absorption of ink by a blotting paper is due to
capillary action, as the blotting paper is porous. When it is
placed over the ink, the ink raises into the pores. Also rise
of oil in the wick of a lamp is due to capillary action.
 If one end of a towel is dipped into a bucket of water and
the other end hangs over the bucket, the entire towel soon
becomes wet due to capillary action.
 Supply of water to the leaves at the top of even a tall tree
is through capillary rise.

10.  A fabric can be waterproof, by adding suitable
waterproofing materials to the fabric. This addition
increases the angle of contact, thereby making the fabric
waterproof.

11. Fluids
Liquids and gases are both fluids:
a fluid is any substance that flows and takes the
shape of its container.

12. Fluids
 The science and technology of the mechanical
properties of liquids is called hydraulics.
 Similarly, the science and technology of the
mechanical properties of air and other gases is
called pneumatics.

13. Compressibility
Gases are therefore highly
compressible: their particles can be
forced back closer together.

14. Density
This means that their density, their mass per unit volume,
is variable.
Density has units of kg/m3.
VDm
V
m
D 

15. Surface Tension

16. Definition
 The net effect is that the molecules at the surface
of the liquid experience an inward force toward the
bulk.
 Such a force pulls the molecules of the interface
together and, as a result, contracts the surface,
resulting in a surface tension.

17.  This “tension” in the surface is the force per unit
length that must be applied parallel to the surface
so as to counterbalance the net inward pull.
 Interfacial tension is the force per unit length
existing at the interface between two immiscible
liquid phases and.
 the surface and interfacial tensions, have the units
of dynes/cm or N/m.

18. Surface Free Energy and Surface Tension
 The surface layer of a liquid possesses additional
energy as compared to the bulk liquid.
 This energy increases when the surface of the same
mass of liquid increases and is therefore
called surface free energy.

19. Viscosity

20. Velocity Gradient
 The resistance tends to keep the fluid in
place.
 Law of inertia
 The fluid moves most near the object and
least farther away.
 This is a velocity gradient.
yvx 
yvx
F

21. Law of Viscosity
 Newton combined these two
proportionalities.
 This is the law of viscosity.
 A is the area of the solid sliding on the fluid
 The constant h is the dynamic viscosity and
depends on the type of fluid.
y
v
AF x
h
yvx
F

22. Drag Force
 Objects falling through a fluid
reach terminal velocity.
 For low speeds this is due to
viscocity.
 Stokes’s Law describes the drag
force.
rvFd h6
Fg
Fb
Fd

23. THANK YOU