Ethiopian Construction Vacancy & Tender

👉HYDRAULICS QUIZ

💫1. Calculate the flow velocity using the continuity equation.
Given:
• Diameter at section 1 = 0.3 m,
• Velocity at section 1 = 4 m/s
• Diameter at section 2 = 0.15 m

Find the velocity at section 2.
Options:
A) 8 m/s
B) 12 m/s
C) 16 m/s ✅
D) 18 m/s
E) 20 m/s
Solution:
Using the continuity equation:
A₁V₁ = A₂V₂
(π/4) (0.3) ² × 4 = (π/4) (0.15) ² × V₂
(0.09) × 4 = (0.0225) × V₂
0.36 = 0.0225 × V₂
V₂ = 0.36 / 0.0225 = 16 m/s

💫2. A pipe with a diameter of 0.2 m carries water at a velocity of 3 m/s. What is the discharge?
Options:
A) 0.094 m³/s ✅
B) 0.050 m³/s
C) 0.125 m³/s
D) 0.070 m³/s
E) 0.200 m³/s
Solution:
Q = A × V = (π/4) (0.2) ² × 3 = (0.0314) × 3 = 0.094 m³/s

❇️3. Calculate the pressure head if the pressure at a point is 150 kPa. (Take ρ = 1000 kg/m³, g = 9.81 m/s²)
Options:
A) 10 m
B) 15.3 m
C) 20.4 m
D) 25.6 m ✅
E) 30 m
Solution:
h = P / (ρg) = 150,000 / (1000 × 9.81) = 25.6 m

💫4. Water flows at 2 m/s through a 100 mm diameter pipe. Find the Reynolds number. (Kinematic viscosity = 1×10⁻⁶5 m²/s)
Options:
A) 150,000
B) 200,000
C) 100,000 ✅
D) 50,000
E) 250,000
Solution:
Re = (V × D) / ν = (2 × 0.1) / (1×10⁻⁶) = 200,000
(Correct answer actually should be B)
✅ Corrected: B) 200,000

💫5. A tank drains water through a 0.1 m diameter orifice at its base. If water level is 4 m high, find the velocity at exit.
Options:
A) 5.6 m/s
B) 6.2 m/sy
C) 8.9 m/s ✅
D) 9.8 m/s
E) 10.5 m/s
Solution:
V = √(2gh) = √(2×9.81×4) = √78.48 = 8.9 m/s

💫6. Determine the head loss in a 50 m long pipe with a flow velocity of 2 m/s, friction factor f = 0.02, and diameter = 0.1 m.
Options:
A) 2.0 m
B) 3.5 m
C) 4.08 m ✅
D) 5.2 m
E) 6.1 m
Solution:
hₗ = f(L/D)(V²/2g) = 0.02 × (50/0.1) × (2² / 2×9.81)
= 0.02 × 500 × (4 / 19.62) = 10 × 0.204 = 2.04 m
✅ Corrected Answer: A) 2.04 m

💫7. If velocity = 3 m/s, area = 0.5 m², what is the flow rate Q?
Options:
A) 1.5 m³/s ✅
B) 0.3 m³/s
C) 6.0 m³/s
D) 3.5 m³/s
E) 2.0 m³/s
Solution:
Q = A × V = 0.5 × 3 = 1.5 m³/s

💫8. A hydraulic jump occurs with initial depth y₁ = 0.3 m and velocity V₁ = 6 m/s. What is Froude number? (g = 9.81 m/s²)
Options:
A) 1.5
B) 2.0
C) 3.4 ✅
D) 4.1
E) 5.0
Solution:
Fr = V₁ / √(g × y₁) = 6 / √(9.81 × 0.3) = 6 / √2.943 = 6 / 1.715 = 3.4

💫9. The discharge over a rectangular notch is 0.8 m³/s, width = 1 m, head = 0.4 m. Find coefficient of discharge Cd.
Options:
A) 0.5
B) 0.6
C) 0.62
D) 0.65
E) 0.64 ✅
Solution:
Q = (2/3)Cd × b × √(2g) × H^(3/2)
0.8 = (2/3)Cd × 1 × √(2×9.81) × (0.4)^(3/2)
0.8 = 0.6667 × Cd × 4.43 × 0.253
0.8 = Cd × 0.749
Cd = 0.8 / 0.749 = 0.64

❇️10. A reservoir has an area of 1000 m². If inflow rate is 2 m³/s and outflow is 1.5 m³/s, what is the rate of rise in water level?
Options:
A) 0.0005 m/s ✅
B) 0.001 m/s
C) 0.002 m/s
D) 0.005 m/s
E) 0.01 m/s
Solution:
Net inflow = 2 - 1.5 = 0.5 m³/s
Rate of rise = 0.5 / 1000 =0.0005 m/s

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