(SEM I) THEORY EXAMINATION 2017-18 ELEMENTS OF MECHANICAL ENGINEERING

This is a complete Engineering Mechanics and Basic Thermodynamics question paper designed as per the 70-mark university examination pattern. The paper covers essential first-year engineering topics such as:

Centroid & Center of Gravity

Coplanar Force Systems

Trusses & Beams

Bending Stress & Torsion

Rankine Cycle

First Law & Zeroth Law of Thermodynamics

Refrigeration & Heat Pumps

Internal Energy, Work & Equilibrium

Concepts of Continuum, Quasi-static Processes

Engineering Applications such as engines, compressors, refrigerators

The paper is divided into three major sections (A, B, and C) and includes numerical problems, derivations, conceptual questions, and diagram-based explanations.
Perfect for B.Tech First Year (ME, CE, AE, EEE, ECE, CSE – Mechanics/Thermo modules).

SECTION A – Short Conceptual Questions (7 × 2 = 14 Marks)

This section checks understanding of basic principles in mechanics and thermodynamics:

Difference between centroid and center of gravity

Equilibrium equations for coplanar concurrent forces

Definition of statically determinate beams

Perfect vs imperfect truss

Zeroth law of thermodynamics

Coefficient of Performance (COP) of a refrigerator

Meaning of dryness fraction (quality of steam)

These questions help build foundation and clarify conceptual basics.

SECTION B – Descriptive Questions (Attempt Any 3 × 7 = 21 Marks)

Parallel Axis Theorem

Statement + mathematical proof.

Truss Explanation

Definition, uses, and assumptions used in truss analysis.

Section Modulus & Polar Modulus

Definition + examples for beams and shafts.

Energy as a Property

Proof using thermodynamic relations.

Rankine Cycle

All four processes (1–2–3–4) explained with a neat T–S diagram.

This section strengthens theoretical concepts with logic and diagrams.

SECTION C – Long Questions (7 Marks Each)

Q3 – Mechanics Numericals

Choose one:

Option (a)

Two spheres in a horizontal channel

Find reactions at points A, B, and C using geometry and statics

Option (b)

Moment of inertia of an I-section about centroidal x and y axes

Q4 – Trusses & Beam Diagrams

Choose one:

Option (a)

Calculate forces in members of a given truss

Option (b)

Draw the Shear Force Diagram (SFD) and Bending Moment Diagram (BMD) of the given beam

Q5 – Bending & Torsion

Choose one:

Option (a)

Derivation of bending equation:

MI=σy=ER\frac{M}{I} = \frac{\sigma}{y} = \frac{E}{R}IM​=yσ​=RE​

Option (b)

Power transmission by solid shaft

Find shaft diameter using torsion formula + angle of twist criteria

Q6 – Thermodynamics

Choose one:

Option (a)

Define:

Thermodynamic equilibrium

Quasi-static process

Concept of continuum

Option (b)

Air compressor steady-flow energy equation

Compute shaft work input using first law of thermodynamics

Q7 – Refrigeration & IC Engines

Choose one:

Option (a)

Domestic food freezer problem

Apply COP of refrigerator to find minimum power required

Option (b)

Working of 4-stroke diesel engine

Neat diagram with labelled strokes: suction, compression, power, exhaust