Hydraulics Objective Questions Flashcards
Fluid is a substance that
cannot remain at rest under action of any shear force
Density of water is maximum at
4 degrees Celsius
Property of a fluid by which its own molecules are attracted is called
cohesion
Property of a fluid by which molecules of different kinds are attracted to each other is called
adhesion
The normal stress in a fluid will be constant in all direction at a point only if
it is at rest
Specific weight of sea water is more that of pure water because it contains
dissolved air, dissolved salt, and suspended matter
Free surface of a liquid tends to contract to the smallest possible area due to force of
surface tension
A liquid would wet the solid, if adhesion forces, as compared to cohesion forces are
more
Barometer is used to measure
atmospheric pressure
Manometer is used to measure
pressure in pipes, channels etc
If cohesion between molecules of a liquid is greater than adhesion between fluid and glass, then the free level of fluid in a dipped glass tube will be
lower than the surface of a liquid
When a fluid is subjected to resistance, it undergoes a volumetric change due to
compressibility
Liquids transmit pressure equally in all the directions. This is according to
Pascal’s Law
The rise or depression of a liquid in a tube due to surface tension with an increase in size of tube will
decrease
Mercury is often used in barometer because
(1) the height of barometer will be less (2) its vapor pressure is so low that it may be neglected
The point in the immersed body through which the resultant pressure of the liquid may be taken to act is known as
center of pressure
Which of the following is the correct relation between centroid (cg) and the center of pressure (cp) of a plane submerged in a liquid?
cp is either at cg or below it
The total pressure force on a plane area is equal to the area multiplied by the intensity of pressure at the centroid, if
(1) the area is horizontal, (2) the area is vertical, (3) the area is inclined
Choose the wrong statement (1) The horizontal component of the hydrostatic force on any surface is equal to the normal force on the vertical projection of the surface, (2) The horizontal component acts through the center of pressure for the vertical projection, (3) The vertical component of the hydrostatic force on any surface is equal to the weight of the volume of the liquid above the area, (4) The vertical component passes through the center of pressure of the volume
Statement 4 is the wrong statement (Explanation: The statement is wrong because the “center of pressure” is typically associated with the resultant of a pressure distribution acting on a surface (like a submerged surface in a fluid), not a volume.)
Center of pressure on an inclined plane is
below the centroid
Can the center of pressure for a vertical plane submerged surface ever be above the center of gravity?
No
In a vertically submerged plane surface, pressure at every point remains the same.
False
For an inclined plate, the pressure intensity at every point differs
True
The magnitude of total pressure and center of pressure is independent on the shape of the submerged plane surface.
False
What is the variation of total pressure with depth for any submerged surface if we neglect variation in the density?
Linear
The resultant upward pressure of a fluid on a floating body is equal to the weight of the fluid displaced by the body. This definition is according to
Archimedes’ Principle
The resultant upward pressure of the fluid on an immersed body is called
buoyant force
What is the principal cause of action of buoyant force on a body submerged partially or fully in fluid?
Displacement of fluid due to submerged body
The center of gravity of the volume of the liquid displaced by an immersed body is called
center of buoyancy
The horizontal component of buoyant force is
zero
The line of action of the buoyant force acts through the
centroid of the displaced volume of fluid
Choose the wrong statement (1) Any weight, floating or immersed in a liquid, is acted upon by a buoyant force, (2) Buoyant force is equal to the weight of the liquid displaced, (3) The point through which buoyant force acts, is called the center of buoyancy, (4) Center of buoyancy is located above the center of gravity of the displaced liquid.
Statement 4 is the wrong statement (Explanation: For a floating object: The center of buoyancy is always above the center of gravity of the object itself. This ensures that the object is stable and doesn’t tip over. For a submerged object: The center of buoyancy is always below the center of gravity of the object itself. This ensures that the object doesn’t rise to the surface. In summary, the center of buoyancy is always related to the center of gravity of the object, not the displaced liquid.)
According to the principle of buoyancy, a body totally or partially immersed in a fluid will be lifted up by a force equal to
the weight of the fluid displaced by the body
How can relatively denser objects be made to float on the less dense fluid?
by altering the shape (Explanation: By altering the shape of a denser object, we can increase its volume without significantly increasing its mass. This means the object will displace a larger volume of fluid, generating a greater buoyant force.)
The conditions for the stable equilibrium of a floating body are
the metacenter should lie above the center of gravity, the center of buoyancy and the center of gravity must lie on the same vertical line, a righting couple should be formed
Metacentric height is given as the distance between
the center of gravity of the body and the metacenter
Metacenter is the point of intersection of
buoyant force and the centerline of body
When a body floating in a liquid, is displaced slightly, it oscillates about
metacenter
When the ship’s metacenter and center of gravity coincide at same point then the vessel is said to be in
neutral equilibrium
Energy gradient line takes into consideration
potential, kinetic and pressure heads
Hydraulic gradient line takes into consideration
potential and pressure heads only
Which of the following is true? (1) EGL always remains constant in the direction of flow (2) EGL always rises in the direction of flow (3) EGL always drops in the direction of flow (4) EGL may or may not change in the direction of flow
Statement 3 is true
Which of the following is true? (1) HGL will never be under EGL (2) HGL will never be above EGL (3) HGL will never coincide with EGL (4) HGL will may or may not be above EGL
Statement 2 is true
The vertical intercept between EGL and HGL is equal to
kinetic head
The slope of HGL will be
equal than that of EGL for a pipe of uniform cross section
Equation of continuity is based on the principle of conservation of
mass
Bernoulli’s equation deals with the law of conservation of
energy
All the terms of energy in Bernoulli’s equation have dimension of
length
The losses of energy in pipes occurs due to
friction of surface, sudden enlargement or contraction of area, any obstruction in the path of flow
The major loss of energy in long pipes is due to
friction
Which one of the following is a major loss?
frictional loss
Minor losses occur due to
sudden enlargement in the pipe, sudden contraction in the pipe, bends in pipe
Minor losses do not make any serious effect in
long pipes
In series pipe problems
the discharge is the same through each pipe
Which of the following conditions is valid in the case of flow through parallel pipes?
The rate of discharge in the main line is equal to the sum of discharges in each of the parallel pipes
Two pipe systems are said to be equivalent when
head loss and discharge are same in two systems
The ratio of absolute viscosity to mass density is known as
kinematic viscosity
The magnitude of water hammer effect in a pipe depends on
speed at which the valve is closed, length of the pipe, elastic properties of the pipe material
The phenomenon of water hammer takes place in pipes
when fluid is suddenly brought to rest by closing the valve
Water hammer pressure can be considerably reduced using
slow closing valves
The ratio of inertia force and gravitational force is called as ______
Froude’s number
Which geometric parameter determines the efficiency of the channel?
Hydraulic radius
For a channel to be economic, which of the following parameters should be minimum?
Wetted perimeter
What is the depth of flow in case of the most economical circular section considering maximum velocity?
0.81D
Differential manometer is used to measure
Difference of pressure between two points
Non uniform flow occurs when
Velocity, depth, pressure, etc. change from point to point in the fluid flow
When a tube of smaller diameter is dipped in water, the water rises in the tube with an upward __________ surface.
concave
The tendency of a liquid surface to contract is due to the following property
Surface tension
The pressure measured with the help of a pressure gauge is called
Gauge pressure
Capillary action is due to the
surface tension, cohesion of the liquid, adhesion of the liquid molecules and the molecules on the surface of a solid
The intensity of pressure on an immersed surface __________ with the increase in depth
Increases
Free surface of a liquid behaves like a sheet and tends to contract to smallest possible area due to the
force of cohesion
The hydraulic gradient line lies over the centerline of the pipe by an amount equal to the
pressure head
