Q.1) Cavitation is primarily associated with which of the following fluid properties :
A) Surface Tension
B) Vapour Pressure
C) Specific Gravity
D) Viscosity
Option (B)
Explanation :
Surface Tension : The ability of a liquid’s surface to withstand an external force is known as surface tension. The reason for this is due to the unequal attraction of molecules in the liquid’s surface, which generates an inward force at the surface and makes the liquid behave as if its surface were covered with a stretched elastic membrane. Because of this tension, the liquid may form droplets, keep objects on its surface, and even permit insects to move across it.
Vapour Pressure : Vapour pressure is the pressure exerted by a vapour in equilibrium with its liquid or solid form. It is the pressure of the vapour when the liquid and vapour are in equilibrium with each other. Vapour pressure is directly related to the temperature of the liquid or solid and is a measure of the amount of vapour present.
Specific gravity : It is the ratio of the density of a substance to the density of a reference substance, usually water.
Viscosity : Viscosity is a measure of a resistance of flow of a fluid. It is the property of a fluid that causes it to resist deformation when subjected to a shearing force.
Q.2) An ideal flow of a liquid obeys –
A) Newton’s law of viscosity
B) Newton’s second law of motion
C) Continuity equation
D) Dynamic viscosity law
Option (C)
Explanation :
An ideal flow of a fluid will always satisfy continuity equation.
Continuity Equation :
Q1 = Q2
ρ1A1V1 = ρ2A2V2
Q.3) Hygrometer is used for estimating :
A) Water content of soil
B) Water vapour content of air
C) Capillary potential of soil water
D) Specific gravity of a liquid
Option (B)
Explanation :
An instrument called a hygrometer is used to gauge the air’s relative humidity. The difference between the amount of moisture in the air and the maximum amount of moisture that the air can hold at a particular temperature is known as relative humidity.
Hygrometers can be analogue or digital and exist in a variety of configurations, such as electronic, psychrometric, and hair hygrometers. They are frequently used in weather stations, greenhouses, museums, and other locations where precise humidity monitoring is crucial.
Q.4) The angle of contact between pure water and clean glass is –
A) 900
B) 450
C) 1300
D) 00
Option (D)
Explanation :
Nil.
Q.5) The space between two parallel plates kept 3mm apart is filled with oil of dynamic viscosity 0.2 Pa sec. What is the shear stress on the lower fixed plate, if the upper one is moved with a velocity of 1.5 m/s?
A) 10
B) 100
C) 1000
D) 0.1
Option (B)
Explanation :
du/dy = 1.5/0.003
τ = μ (du/dy) [Newton’s law of viscosity]
τ = 0.2 * (1.5/0.003) = 100 N/m2
Q.6) A flow is called hypersonic, if the Mach number is –
A) < 6
B) > 6
C) > 1
D) < 1
Option (B)
Explanation :
Mach number for different conditions :
Sub-sonic : < 1
Sonic : = 1
Super-sonic : > 1
Hyper-sonic : > 6
Q.7) A fluid which is incompressible and has no viscosity is known as :
A) Ideal fluid
B) Newtonian fluid
C) Non-newtonian fluid
D) Real fluid
Option (A)
Explanation :
Ideal fluid : An ideal fluid is a theoretical fluid that has no viscosity, incompressible, no resistance to flow and the fluid flows at a constant velocity in response to an applied force. Ideal fluids are used as a basis for theoretical calculations in fluid dynamics, but they do not exist in reality.
Newtonian fluid : Newton’s law of viscosity, which states that the shear stress applied to the fluid is directly proportional to the rate of change in velocity with respect to time, is followed by a Newtonian fluid, a category of real fluid. This indicates that the fluid’s viscosity is constant and independent of the fluid’s velocity, and that there is a linear relationship between the shear stress and the rate of strain. Many liquids, including water, are regarded as Newtonian fluids.
Non-Newtonian fluid : A real fluid that deviates from Newton’s law of viscosity and does not display a linear correlation between shear stress and rate of strain is known as a non-Newtonian fluid. Instead, a non-Newtonian fluid’s viscosity is governed by the rate of deformation and is susceptible to variations in shear stress. Ketchup, paint, and blood are a few typical examples of non-Newtonian fluids.
Real fluid : A real fluid is a type of fluid that exists in the real world and is subject to various physical and chemical forces. Unlike ideal fluids, real fluids have viscosity and are compressible. They can be either Newtonian or non-Newtonian fluids. The behavior of real fluids is more complex than that of ideal fluids, and it can be affected by various factors, such as temperature, pressure, and chemical composition.
Q.8) The flow in a capillary tube is laminar because –
A) the capillary tube is made of glass
B) the surface tension and capillarity promote laminarisation
C) the diameter of the capillarity tube is very small
D) None of the above
Option (C)
Explanation :
The flow in a capillary tube is laminar flow because the diameter of the capillary tube is very small. If the diameter of the capillary tube is large then there will be turbulence in the capillary tube and laminar will not occur.
Q.9) A floating body is said to be in a state of stable equilibrium :
A) The Metacentre M coincides with the centre of gravity G
B) The metacentre M is above centre of gravity G
C) The metacentre M is below centre of gravity G
D) The centre of buoyancy B is above centre of gravity G
Option (B)
Explanation :
Stable Equilibrium conditions for a floating body :
- M is above H (GM > 0) = Sable Equilibrium
- M coinciding with G (GM = 0) = Neutral Equilibrium
- M is below G (GM < 0) = Unstable Equilibrium
Q.10) When a ship enters sea from river, one can expect to to :
A) sink a little
B) rise a little
C) remain at the same level of the draft
D) sink if the temperature difference between the river and seawater is more than 2 deg celsius.
Option (B)
Explanation :
When a ship enters a sea from a river, the ship is elevated or uplifted due to the density of sea water and during the buoyant motion of the ship, as it would gain both potential and kinetic energy when rising a little fluid.
Q.11) A point through which the force of buoyancy is supposed to act :
A) Buoyancy
B) Centre of buoyancy
C) Metacentric height
D) Metacentre
Option (B)
Explanation :
The center of buoyancy is the point at which the entire buoyant force on an object acts, and is calculated as the average location of all the buoyant forces acting on an object. In other words, it is the point at which the object appears to be balanced in the water or any other fluid.
The geometric centre of the part of a floating object that is submerged in the fluid is where the centre of buoyancy for that object is located. The object’s shape, orientation, and the fluid it is submerged in all affect where the centre of buoyancy is located.
The centre of buoyancy is a key idea in naval architecture and ship design since it has an impact on a ship’s stability. The stability of the ship is determined by the location of the centre of buoyancy in relation to the centre of gravity, and it is utilised in the design of ships to guarantee that they are stable and safe to operate.
Q.12) Multi U-tube manometers with different fluids are used to measure –
A) Very low pressure
B) Medium pressure
C) Low pressure
D) High pressure
Option (D)
Explanation :
Nil.
Q.13) Pressure of fluid is measured by :
A) Lactometer
B) Barometer
C) Manometer
D) Thermometer
Option (C)
Explanation :
Functions of different devices :
Manometer : Used to measure pressure of fluids.
Thermometer : Used to measure temperature.
Barometer : Used to measure atmospheric pressure.
Lactometer : Used to measure quality of milk.
Q.14) The average value of the co-efficient of velocity is –
A) 0.62
B) 0.84
C) 0.76
D) 0.97
Option (D)
Explanation :
The ratio of actual velocity of the jet at vena-contracta to the theoretical velocity is known as coefficient of velocity.
Coefficient of velocity (Cv) = 0.97
Coefficient of contraction (Cc) = 0.64
Coefficient of discharge (Cd) = 0.61 to 0.64
Q.15) The major loss of hydraulic energy in pipe flow occurs in long pipe due to –
A) Sudden enlargement
B) Friction
C) Sudden contraction
D) Gradual enlargement or contraction
Option (B)
Explanation :
Head loss, HL = (flV2)/(2gD)
f = friction factor
l = length of pipe
V = velocity of flow through pipe
Q = discharge
g = acceleration due to gravity
D = diameter of pipe
Q.16) The sluice valves used for dewatering the pipe line are called :
A) Safety valve
B) Scour valve
C) Discharge control valve
D) Sectionalizing valve
Option (B)
Explanation :
Nil.
Q.17) A pitot tube is used to measure the velocity of water in the pipe. The stagnation pressure head is 6m and the static pressure head is 5m. Calculate the velocity of flow assuming the coefficient of the tube is equal to 0.98.
A) 8.92 m/s
B) 4.34 m/s
C) 5.05 m/s
D) 11.15 m/s
Option (B)
Explanation :
v = Cd * √(2gh) = 0.98*√(2*9.81*1) = 4.34 m/s.
h = stagnation pressure head – static pressure head = 6 – 5 = 1 m.
Q.18) The purpose of surge tank is –
A) To regulate flow of water to turbines by providing necessary retarding head of water
B) To eliminate water hammer possibilities
C) To control the pressure variations due to rapid changes in the pipeline flow
D) All of the above
Option (D)
Explanation :
Nil.
Q.19) A point in a compressible flow, where the velocity of fluid is zero, is called :
A) Critical point
B) Stagnation point
C) Vena-contracta
D) None of the above
Option (B)
Explanation :
The stagnation point is the point in compressible fluid where the velocity of fluid is zero.
Q.20) Study of flow net enables us to –
A) estimate the velocity of variations
B) find the velocity at all points
C) estimate the pressure at all points
D) determine the energy loss in flow
Option (D)
Explanation :
Nil.
