In a U-tube manometer measuring differential pressure, if one side contains mercury (ρ = 13600 kg/m³) with a height difference of 250 mm, what is the differential pressure?
Answer: B
ΔP = ρ_mercury × g × h = 13600 × 9.81 × 0.25 = 33,324 Pa ≈ 33.3 kPa
Q.62Easy
The relative roughness of a pipe is defined as:
Answer: B
Relative roughness ε/D = (absolute roughness)/(pipe diameter). This dimensionless parameter determines flow behavior in the Moody chart for turbulent flow calculations.
Q.63Easy
A centrifugal pump operates with water (ρ = 1000 kg/m³) at an impeller diameter of 0.3 m and rotational speed of 1500 RPM. Calculate the peripheral velocity at the impeller tip.
Answer: A
Peripheral velocity = π × D × N / 60 = π × 0.3 × 601500 = 23.56 m/s
Q.64Easy
In laminar flow through a circular pipe, the velocity profile is parabolic. What is the ratio of average velocity to maximum velocity at the centerline?
Answer: B
For laminar flow in circular pipes, v_avg = v_max/2, so the ratio is 0.5
Q.65Easy
Which dimensionless number characterizes the relative importance of inertial forces to viscous forces in fluid flow?
Answer: B
Reynolds number (Re = ρVD/μ) represents the ratio of inertial to viscous forces
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Q.66Easy
In a reciprocating pump with piston diameter D = 0.1 m and stroke length L = 0.2 m operating at 60 RPM, calculate the theoretical displacement per revolution.
Answer: A
Displacement = π/4 × D² × L = π/4 × (0.1)² × 0.2 = 0.00157 m³ per revolution
Q.67Easy
A fluid flows through a circular pipe of diameter 50 mm at a velocity of 2 m/s. If the kinematic viscosity is 1×10⁻⁵ m²/s, calculate the Reynolds number and identify the flow regime.
Answer: A
Reynolds number = (ρVD)/μ = VD/ν = (2 × 0.05)/(1×10⁻⁵) = 10,000. Flow is turbulent for Re > 4,000.
Q.68Easy
Which of the following dimensionless numbers represents the ratio of inertial forces to viscous forces in fluid flow?
Answer: B
Reynolds number (Re) = inertial forces/viscous forces. It is the fundamental dimensionless number in fluid mechanics.
Q.69Easy
In a horizontal pipe flow, the pressure drop increases with which of the following factors?
Answer: C
Pressure drop (Δp) is proportional to friction factor which increases with pipe roughness. From Hagen-Poiseuille and Darcy equations, rougher pipes cause higher friction losses.
Q.70Easy
A centrifugal pump has an impeller diameter of 0.3 m rotating at 1500 RPM. Calculate the peripheral speed of the impeller tip.
The net positive suction head (NPSH) available is 4.5 m and NPSH required is 3.2 m for a pump. What can be concluded?
Answer: B
Cavitation occurs when NPSH available < NPSH required. Here 4.5 > 3.2, so cavitation is prevented and pump operates safely.
Q.72Easy
Which pump characteristic curve represents the relationship between head and flow rate?
Answer: A
The H-Q (head vs flow rate) curve is the primary pump characteristic curve that shows how head decreases as flow rate increases.
Q.73Easy
In compressible flow through a nozzle, sonic or critical conditions occur when Mach number equals:
Answer: B
Critical or sonic conditions occur at Mach number = 1.0, where velocity equals the speed of sound in the fluid.
Q.74Easy
In a fluid flow system, which of the following best represents the Bernoulli equation?
Answer: B
Bernoulli equation in head form: P/ρg + V²/2g + Z = constant. Option A is energy form, C is Darcy-Weisbach, D is modified form.
Q.75Easy
The Reynolds number for a fluid flow is defined as the ratio of inertial forces to viscous forces. For a pipe flow with diameter 0.05 m, velocity 2 m/s, and kinematic viscosity 1.0×10⁻⁶ m²/s, calculate the Reynolds number.
Answer: A
Re = (V×D)/ν = (2×0.05)/(1.0×10⁻⁶) = 0.1/(1.0×10⁻⁶) = 100,000
Q.76Easy
Which of the following statements about laminar flow in a circular pipe is correct?
Answer: B
In laminar flow through circular pipes, the velocity distribution follows Hagen-Poiseuille flow with parabolic profile. Maximum velocity is at the centerline (V_max = 2×V_avg), and velocity is zero at the wall (no-slip condition).
Q.77Easy
A fluid flows through a horizontal pipe of diameter 0.1 m at a velocity of 3 m/s. If the pipe suddenly contracts to 0.05 m diameter, what is the velocity in the contracted section (assuming incompressible flow)?
The friction factor 'f' in the Darcy-Weisbach equation depends on Reynolds number and relative roughness. For laminar flow (Re < 2300), friction factor is given by:
Answer: A
For laminar flow in circular pipes, the Hagen-Poiseuille solution gives f = 64/Re. This is independent of roughness and applies for Re < 2300.
Q.79Easy
A manometer shows a pressure difference of 50 mm of mercury (ρ_Hg = 13,600 kg/m³). What is the equivalent pressure difference in Pa?
Answer: A
ΔP = ρ_Hg × g × h = 13,600 × 9.81 × 0.05 = 6,667 Pa
Q.80Easy
For a fluid flowing over a submerged object, the drag force is given by F_D = (21)ρV²AC_D. If velocity doubles and drag coefficient remains constant, drag force increases by a factor of:
Answer: B
F_D ∝ V². When V doubles (V₂ = 2V₁), F_D increases by factor of (2)² = 4
