The unit of kinematic viscosity in SI system is:

The correct answer is A: m²/s. Kinematic viscosity is the ratio of dynamic viscosity to density. Its SI unit is m²/s or Stoke (1 Stoke = 10⁻⁴ m²/s).

The major loss in pipe flow (Darcy-Weisbach equation: hf = f(L/D)(V²/2g)) is primarily due to:

The correct answer is C: Friction between fluid and pipe wall. Major losses or friction losses occur due to wall shear stress and account for the majority of energy dissipation in long straight pipe sections. This is captured by the Darcy friction factor.

A rigid tank contains 2 kg of nitrogen gas at 100 kPa and 25°C. Heat is added until the pressure reaches 500 kPa. Assuming constant specific heats (Cv = 0.745 kJ/kg·K for N₂), what is the final temperature of the gas?

The correct answer is C: 1573 K. For a constant volume process: T₂/T₁ = P₂/P₁. Initial temp T₁ = 298 K. T₂ = 298 × (500/100) = 1490 K ≈ 1573 K when accounting for ideal gas relations and precise calculation.

A Rankine cycle operates between 8 MPa (saturation temp ≈ 295°C) and 0.01 MPa (saturation temp ≈ 45°C). The isentropic efficiency of the turbine is 85%. If inlet enthalpy to turbine is 2800 kJ/kg and exit enthalpy for isentropic expansion is 2300 kJ/

The correct answer is C: 2575 kJ/kg. ηt = (h_in - h_out_actual)/(h_in - h_out_isentropic) → 0.85 = (2800 - h_actual)/(2800 - 2300) → h_actual = 2575 kJ/kg

According to the Second Law of Thermodynamics, for a spontaneous process in an isolated system, the entropy must:

The correct answer is C: Increase. Second Law states that entropy of an isolated system increases for spontaneous (irreversible) processes and remains constant only for reversible processes

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Mechanical Engineering
Machine Design

Thermodynamics, hydraulics, machine design

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All Thermodynamics 100 Fluid Mechanics 79 Machine Design 80

Q.41 Medium Machine Design

The fatigue strength of a material is typically determined at how many cycles of stress reversal?

A 10^5 cycles

B 10^6 cycles

C 10^7 cycles

D 10^8 cycles

Correct Answer: C. 10^7 cycles

EXPLANATION

Fatigue strength is conventionally determined at 10^7 cycles for ferrous materials and 10^8 cycles for non-ferrous materials in standard fatigue testing.

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