Allied & ICAR Exam Bank • ALLIED_0128 MCQ • 1 Mark

Section 2: Farm Machinery

Machine Design

Subtopic: Measurement of force, stress, torque, speed, displacement and acceleration on machine elements – shafts, couplings, keys, bearings and knuckle joints

Question Statement:

In hydrodynamic journal bearings used in engine crankshafts, the dimensionless Sommerfeld number $S$ is given by:

Options:

  • (A) $\left(\frac{r}{c}\right)^2 \frac{\mu N_s}{P}$
  • (B) $\left(\frac{c}{r}\right)^2 \frac{P}{\mu N_s}$
  • (C) $\frac{\mu N_s}{P}$
  • (D) $\frac{r c \mu}{P N_s}$

Answer Key:

A

Step-by-Step Solution & Explanation

The Sommerfeld number is defined as $S = (r/c)^2 (\mu N_s / P)$, governing the operating regime of hydrodynamic lubrication.
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