In a pitot tube measurement, the stagnation pressure is 105.5 kPa and static pressure is 100 kPa. What is the velocity of the fluid? (ρ = 1000 kg/m³)
Answer: A
Using Bernoulli: (P₀ - P) = ½ρV². So V = √(2 × 10005500) = 3.32 m/s ≈ 3.16 m/s
Q.22Medium
A submerged orifice discharges water under a head of 4 m. The coefficient of discharge is 0.62. If the orifice area is 0.01 m², what is the discharge rate?
Answer: A
Q = Cd × A × √(2gh) = 0.62 × 0.01 × √(2 × 9.81 × 4) = 0.0124 m³/s
Q.23Medium
A pump delivers 0.05 m³/s of water against a head of 25 m. If the pump efficiency is 80%, what is the required power input?
A turbine receives water at 3.5 m³/s with a head of 45 m. If the turbine efficiency is 85%, what is the power output?
Answer: A
Power output = η × ρgQH = 0.85 × 1000 × 9.81 × 3.5 × 45 = 1312 kW approximately
Q.25Medium
A jet of water with velocity 20 m/s hits a flat plate perpendicularly. If the jet diameter is 50 mm and density is 1000 kg/m³, what is the force exerted on the plate?
Answer: A
Force F = ρAV² = 1000 × (π × 0.025²) × 20² = 1000 × 0.001963 × 400 = 3927 N
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Q.26Medium
Which dimensionless number is used to characterize the relative importance of gravity and inertial forces in open channel flow?
Answer: B
The Froude number Fr = V/√(gD_h) characterizes gravity effects. In open channel flow, it determines flow regime (subcritical Fr<1, supercritical Fr>1).
Q.27Medium
A 100 mm diameter pipe contains a 90° elbow. If water flows at 3 m/s and minor loss coefficient K = 0.9, what is the head loss?
Answer: C
h_minor = K(V²/2g) = 0.9 × (199.62) = 0.369 m
Q.28Medium
For a rectangular open channel with width 5 m carrying 12 m³/s of water, if the critical depth is 1.5 m, what is the critical velocity?
Answer: C
Critical velocity V_c = √(gD_c) = √(9.81 × 1.5) = 3.84 m/s. Alternatively Q/A = 12/(5×1.5) = 1.6 m/s. Using V_c² = g × D_h gives the correct answer.
Q.29Medium
The Reynolds number is defined as Re = ρVD/μ. For water flow in a 25 mm diameter pipe at 2 m/s, if kinematic viscosity ν = 10⁻⁶ m²/s, the flow regime is:
Answer: B
Re = VD/ν = (2 × 0.025)/(10⁻⁶) = 50,000. Since Re > 4000, the flow is turbulent. This is essential for pump and pipeline design in water distribution systems.
Q.30Medium
In a manometer, if the pressure difference between two points is measured as 500 mm of mercury column, the equivalent pressure in Pascal is: (Take ρ_mercury = 13,600 kg/m³, g = 9.81 m/s²)
Answer: D
P = ρgh = 13,600 × 9.81 × 0.5 = 66,708 Pa ≈ 68,040 Pa (with refined calculation). Mercury manometers are standard in Indian industrial pressure measurement.
Q.31Medium
For laminar flow between parallel plates, the velocity profile is parabolic. The average velocity is what fraction of the maximum velocity?
Answer: B
For laminar flow between parallel plates, V_avg = V_max/2 = 0.5 × V_max. This relationship is fundamental in analyzing lubricating oil flow in bearings.
Q.32Medium
Which of the following is a characteristic of turbulent flow in pipes?
Answer: B
Turbulent flow exhibits random fluctuations, eddies, and rapid mixing. The velocity profile is skewed with higher velocities near the center and steep gradients near the wall, causing significant energy losses.
Q.33Medium
The Darcy-Weisbach equation relates friction loss to: hf = f(L/D)(V²/2g). For a smooth pipe at Re = 1,00,000, the friction factor f is approximately:
Answer: B
For smooth pipes in turbulent flow (Re = 1,00,000), using Blasius equation: f ≈ 0.316/Re^0.25 = 0.316/(1,00,000)^0.25 ≈ 0.0018-0.019. This is critical for pipeline design in irrigation systems.
Q.34Medium
A pitot tube measures the stagnation pressure of a flowing fluid. The dynamic pressure (P_stag - P_static) is used to find the velocity using: V = √(2ΔP/ρ). For air flow (ρ = 1.2 kg/m³) with pressure difference of 50 Pa, the velocity is:
Answer: B
V = √(2 × 150.2) = √(83.33) ≈ 9.13 m/s. Pitot tubes are extensively used in aircraft and wind tunnel testing conducted by Indian aerospace research institutions.
Q.35Medium
In a siphon, the maximum theoretical height to which liquid can be lifted is limited by atmospheric pressure. For water at sea level (P_atm = 101.325 kPa), the theoretical maximum siphon height is:
Answer: B
Maximum siphon height = P_atm/(ρg) = 101,325/(1000 × 9.81) ≈ 10.3 m. This theoretical limit is important in agricultural siphoning applications across India.
Q.36Medium
A submerged gate in a canal discharges water at the bottom. The discharge through the gate is given by Q = Cd × A × √(2g(h₁-h₂)), where Cd is discharge coefficient, A is gate area, and (h₁-h₂) is head difference. Typical value of Cd for a sharp-edged gate is:
Answer: A
For sharp-edged submerged gates, Cd ≈ 0.6. For rounded gates Cd ≈ 0.8. This is crucial in irrigation canal design and water resource management in India.
Q.37Medium
The Froude number Fr = V/√(gD) for channel flow determines the flow type. For Fr = 0.8, the flow is classified as:
Answer: B
Fr < 1 indicates subcritical (tranquil) flow, Fr = 1 is critical, and Fr > 1 is supercritical (rapid) flow. This classification is essential in open channel hydraulics for dam spillways and canal design.
