Mechanical Engineering - MCQ Practice Questions

A horizontal pipe carries water at steady state. At section 1: P₁ = 200 kPa, V₁ = 3 m/s. At section 2: V₂ = 6 m/s. Assuming ideal incompressible flow and neglecting friction, the pressure at section 2 is:

The Strouhal number is used to characterize:

For compressible flow through a convergent nozzle, chocking occurs when:

In open channel flow, the critical depth occurs when:

For a submerged curved vane deflecting a jet, the component of force in the direction of jet is:

The equivalent length method for minor losses in pipes replaces a fitting with an equivalent length of pipe. For a 90° elbow with diameter 50 mm, typical equivalent length is:

In a centrifugal pump, the impeller diameter is doubled while keeping speed constant. The head capacity changes by factor of:

For a weir with discharge Q = C_w × L × H^($\frac{3}{2}$), if the length is doubled and head is halved, the new discharge becomes:

A vertical pipe of diameter 40 mm has water flowing upward at 2.5 m/s. If the friction factor is 0.035 and pipe length is 50 m, what is the total head loss (friction + elevation)?

A circular jet impinges on a 45° inclined flat plate and splits equally. If jet velocity is 15 m/s and diameter is 30 mm, what is the magnitude of the resultant force?

In a venturi meter, if the area ratio is 4:1 and the pressure difference is 8 kPa, what is the velocity in the throat? (ρ_water = 1000 kg/m³)

A horizontal jet of 0.02 m² cross-section with velocity 8 m/s strikes a curved vane and is deflected 60°. What is the force on the vane in the direction of jet?

The momentum equation for a control volume states that ΣF = d(mV)/dt. For a fluid jet deflected by a flat plate at angle θ to the horizontal, the force perpendicular to the original jet direction depends on:

For a Venturi tube with throat area ratio A₁/A₂ = 3 and upstream pressure P₁ = 200 kPa, assuming inviscid flow (Bernoulli applicable), if the pressure at throat P₂ drops to 80 kPa, the upstream velocity V₁ is (ρ = 1000 kg/m³):

The Mach number M = V/a represents the ratio of flow velocity to the speed of sound. For subsonic compressible flow in a converging nozzle, what occurs to the Mach number as the flow accelerates?

For pipe flow, the friction factor f in the Moody diagram depends on both Reynolds number and relative roughness (ε/D). For a rough pipe with high Re, f approaches an asymptotic value independent of Re. This region is called:

The specific speed of a turbine is Ns = N√Q/H^1.25, where N is speed in rpm, Q is discharge in m³/s, and H is head in meters. A turbine with Ns < 50 is classified as:

According to the theory of boundary layer flow, the boundary layer thickness δ grows along a flat plate as δ ∝ √(νx/V). This relationship is derived from:

The cavitation parameter σ = (P - Pv)/(0.5ρV²) indicates the tendency of a flowing fluid to cavitate. Cavitation occurs when σ drops below a critical value σc. For a given pump, lowering the inlet pressure or raising the fluid temperature will: