Learning Unit 5

Question 1

Mechanics can be divided into three parts. Name the parts.

Answer 1

Mechanics of rigid body Mechanics of solids Mechanics of fluids.

Question 2

There is no internal deformation in the body and we
study about the static and dynamic position of the
body subjected to external forces

Answer 2

Mechanics of rigid body

Question 3

The solid deforms are subjected to external forces and
we study the nature of deformation in the body

Answer 3

Mechanics of solid

Question 4

The shape and size of the body is not constant and we study
about statics and dynamics of flow of fluid subjected to
various types of forces on it.

Answer 4

Fluid Mechanics

Question 5

List three (3) important properties of fluids

Answer 5

Density, viscosity, surface tension, bulk modulus, vapour pressure

Question 6

Define viscosity in terms of flow

Answer 6

Viscosity, μ is a property of fluid which offers resistance to sheer deformation. Different fluids deform
at different rates under the same shear stress . Fluid with a high viscosity, such as lubricant oil deforms
more slowly than fluid with a low viscosity such as water

Question 7

Describe surface tension

Answer 7

Surface tension is the tendency of the surface of a liquid to behave like a stretched elastic membrane.
– There is a natural tendency for liquids to minimize their surface area .
– All liquid molecules exhibit cohesive forces binding them with each other .
– This cohesive bond exhibits a tensile strength for the surface layer and this is known as surface tension

Question 8

Define capillarity

Answer 8

Capillarity is a phenomenon of rise or fall of liquid surface in a small tube relative to the adjacent
general level of liquid when the tube is held vertically in the liquid. The rise of liquid surface is known as
capillary

Question 9

Name and describe four (4) types of flow

Answer 9

Steady and Unsteady Flow: Steady flow is that type of flow in which the fluid characteristics such as
velocity, pressure, density, etc. at a point do not change with time. Unsteady flow is that type of flow in
which the fluid characteristics such as velocity, pressure, density, etc. at a point change with time.
– Uniform and Non-uniform Flow: Uniform flow is that type of flow in which velocity of the fluid does not
change with respect to space. Non-uniform flow is that type of flow in which velocity of the fluid
changes with respect to space.
– Laminar and Turbulent Flow: Laminar flow is that type of flow in which the fluid particles move along
well-defined paths of stream line and all the stream lines are straight and parallel to each other.
Turbulent flow is that type of flow in which fluid particles move in zig-zag way.
Compressible and Incompressible Flow : Compressible flow is that type of flow in which density of fluid
changes from point to point. Incompressible flow is that type of flow in which density of fluid remains
constant throughput the flow.
– Rotational and Irrotational Flow: In rotational flow, fluid particles moving on stream lines also rotate
about their axes. In irrotational flow fluid particles do not rotate about their axes, but they smoothly
move in stream line