Solved question paper for EME May-2014 (B-TECH 1st-2nd)
Solved Question Paper
Elements of mechanical engineering May-2014
PTU • B-TECH • Information Technology • 1st-2nd • May-2014
elements of mechanical engineering previous year question papers on BRpaper are organized for students of Punjab Technical University’s Bachelor of Technology program, 1st-2nd semester. This section makes it easier to browse subject-wise old question papers for elements of mechanical engineering, so students can review how questions are typically framed in past exams and get a sense of the exam pattern. Many students search for elements of mechanical engineering question bank while preparing for exams, and this page is built to support exactly that kind of subject-wise browsing and revision. BRpaper is not the official website of Punjab Technical University or any institution, and it does not publish official notices or academic updates.
PART-A
1. Basic Concepts of Thermodynamics (08)
Definition of thermodynamic: Need to study thermodynamics; Application areas of thermodynamic; Difference between Microscopic (or, Statistical) thermodynamics and Macroscopic(or, Classical) thermodynamics; Brief concept of continuum; Thermodynamic System : definition, types (Open, Closed and Isolated) and their examples; Thermodynamic System Boundary : definition, types and their examples; Surroundings; Control(fixed) mass and Control Volume concept and their example ; Thermodynamic State; Thermodynamic Property: definition, types citing their examples; condition for any quantity to be a property; State postulate; Thermodynamic equilibrium (which includes Thermal, Mechanical and Chemical equilibrium etc.); Thermodynamic path; Thermodynamic process: definition, concept of reversible process, quasi-static (or, quasi-equilibrium) process, irreversible process, conditions for reversibility and how these are met with, non-flow processes and flow processes, method of representation of reversible and irreversible process on property diagrams; Cyclic process; Thermodynamic Cycle: definition and its concept; Energy and its forms (microscopic and macroscopic); Physical insight to internal energy; Energy transfer across system boundary i.e. transient energies (heat and work); Difference between heat and work; Sign conventions for heat and work interactions; heat and work as path functions; Equality of Temperature and Zeroth law of Thermodynamics.
2. First Law of Thermodynamics and its applications (12)
Definition, essence and corollaries or consequences of first law of Thermodynamics; Expressions for First law of Thermodynamics for a control mass undergoing a Cycle and for process (i.e., a change in state of a control mass) ; Concept of Enthalpy and total energy and differentiation between the two - a thermodynamic property; Compressible and incompressible substances, Specific heats, Difference between Internal Energy and Enthalpy of compressible and incompressible substances; Representation of first law of thermodynamics as rate equation; Analysis of non-flow/ flow process for a control mass undergoing constant volume, constant pressure, constant temperature, adiabatic and polytropic processes; Free Expansion Process and its examples, its representation on Property diagram; Review of concepts of control volume; Expressions of first law of thermodynamics for a control volume (i.e. open system) ; Steady State Steady Flow process and its examples; First law analysis of Steady State Flow process e.g. isochoric, isobaric, isothermal, isentropic and polytropic process; Throttling process and its applications; Flow energy or inertial energy of flowing fluids or, Energy transport by mass; Application of Steady State Flow Energy Equation to various engineering devices.
3. Second Law of Thermodynamics (16)
Limitations of first law of thermodynamics; and how 2nd law is fully able to explain away and thus overcome those shortcomings of Ist law; Thermal Reservoirs, source and sink (Low temperature and high temperatures); Heat Engine, Heat Pump and Refrigerator: definitions, working, efficiency/performance and their real life examples. Justification as to why the actual efficiency of Heat Pump and Refrigerator shall also be ≤ 100% though on the face of it seems to be more than 100%; Various statements of Second Law of Thermodynamics and their equivalence; Philosophy of Carnot cycle and its consequences viz. how each of the individual four processes constituting the cycle contribute in optimizing the output and efficiency of the cycle; Carnot Engine, Carnot Refrigerator and Carnot Heat Pump: definitions, working, efficiency/performance and Limitations of the cycle; Carnot theorem for heat engines, refrigerators and heat pumps; derivation of Carnot efficiency/COP (which seems to be more than 100%); Thermodynamic Temperature Scale; Clausius theorem and Inequality; Philosophy and concept of entropy; Entropy changes during various processes; Temperature - Entropy Chart and representation of various processes on it; Principle of Increase of Entropy; Applications of Entropy Principle; Quality of Energy viz. high and low grade energies; Degradation of Energy; Third Law of Thermodynamics.
PART-B
4. Gas Power Cycles (12)
Introduction; Concept and philosophy of Air Standard Cycle alongwith associated assumptions and advantages; Air Standard Efficiency; Nomenclature of reciprocating piston-cylinder arrangement with basic definitions such as swept volume, clearance volume, compression ratio, mean effective pressure etc; Otto Cycle (or constant volume heat addition cycle), Diesel cycle (or constant pressure heat addition cycle) and Dual cycle (Mixed or Composite or Limited Pressure cycle) with their representation on P-V and T-S charts, their Air-standard (thermal) Efficiencies; Brayton Cycle, Comparison of Otto, Diesel and Dual cycle under some defined similar parametric conditions; Introduction to heat engines; Merits of I.C. Engines and their important applications, Classification and constructional features of I.C. Engines; working of two stroke and four stroke Petrol and Diesel engines and their comparison.
5. Engineering Materials (05)
Materials and Civilization, Materials and Engineering, Classification of Engineering Materials, Mechanical Properties of Materials: elasticity, plasticity, strength, ductility, brittleness, melleability, toughness, resilience, hardness, machinability, formability, weldability. Properties, Composition, and Industrial Applications of materials: metals (ferrous- cast iron, tool steels, stainless steels and non ferrous- Aluminum, brass, bronze ), polymers (natural and synthetic , thermoplastic and thermosetting), ceramics (glass, optical fibre glass, cements), composites ( fibre reinforced, metal matrix), smart materials (piezoelectric, shape memory, thermochromic, photochromic, magnetorheological), Conductors, Semiconductors and insulators, Organic and Inorganic materials. Selection of materials for engineering applications.
6. Centroid, Centre of Gravity and Moment of Inertia: (08)
Difference between centre of gravity and centroid. Determination of position of centroid of plane geometric figures of I, U, H, L, T, C, Circular and Triangular Sections. Centroid of Composite Areas. Determination of position of Centre of Gravity (CG) of regular solids viz. Right Circular Cone, Solid Hemisphere, thin Hollow Hemisphere. Area moment of inertia & mass moment of inertia, Polar moment of inertia, Parallel axes Theorem (or transfer formula), Perpendicular axes Theorem, Radius of gyration, determination of area Moment of Inertia of I, U, H, L, T, C, Circular and Triangular Sections along various axes. Mass moment of Inertia of Circular Ring, Disc, Cylinder, Sphere and Cone about their axis of symmetry and other axes.
Solved Questions
Solved-
A constant mass goes through a process where 100 W of heat transfer comes in and 100 W of work leaves. Does the mass change state?Short Answer 2 Marks May-2014 • PTU B-TECH
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An inventor has developed a refrigeration unit that maintains the cold space at -10°C while operating in a 25°C room. A coefficient of performance of 8.5 is claimed. How do you evaluate this?Short Answer 2 Marks May-2014 • PTU B-TECH
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A reversible process adds heat to a substance. If T is varying, does that influence the change in s?Short Answer 2 Marks May-2014 • PTU B-TECH
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For the same compression ratio and heat rejection, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.Short Answer 2 Marks May-2014 • PTU B-TECH
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May 2014 For the same peak pressure, peak temperature and heat rejection, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.
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Dec 2011 For the same maximum pressure and work output, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.
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Dec 2011 For the same maximum pressure and heat input, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.
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For the same peak pressure, peak temperature and heat rejection, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.Short Answer 2 Marks May-2014 • PTU B-TECH
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May 2014 For the same compression ratio and heat rejection, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.
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Dec 2011 For the same maximum pressure and work output, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.
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Dec 2011 For the same maximum pressure and heat input, compare Otto cycle and Diesel cycle on P-v and T-s diagrams.
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In the absence of any friction and other irreversibilities, can a heat engine have an efficiency of 100 percent?Short Answer 2 Marks May-2014 • PTU B-TECH
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May 2014 In the absence of any friction and other irreversibilities, can a heat engine have an efficiency of 100 percent? Explain.
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Define the following: i) Resilience, ii) Proof resilience, iii) Modulus of resilience.Short Answer 2 Marks May-2014 • PTU B-TECH
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May 2018 Define resilience, proof resilience and modulus of resilience.
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May 2012 Define resilience, proof resilience and modulus of resilience.
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For a material, Young’s modulus is given as 1.2 x 10^5 N/mm^2 and Poisson’s ratio is 0.25. Calculate the bulk modulus.Short Answer 2 Marks May-2014 • PTU B-TECH
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Draw neat sketches of any two inversions of double slider kinematic chain.Short Answer 2 Marks May-2014 • PTU B-TECH
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Dec 2011 Draw neat sketches of any two inversions of four bar kinematic chain?
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Explain the terms reversibility and irreversibility as applied to lifting machines.Short Answer 2 Marks May-2014 • PTU B-TECH
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May 2016 Discuss the reversibility of lifting machines.
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A system containing 0.2 m^3 of air at a pressure of 4 bar and 160°C expands isentropically to a pressure of 1.06 bar and this gas is heated at constant pressure till the enthalpy increases by 65 kJ. Calculate the work done. Now imagine that these processes are replaced by a single reversible polytropic process producing the same work between initial and final state; find the index of expansion in this case. Take c_p = 1.005 kJ/kg-K.Long Answer 8 Marks May-2014 • PTU B-TECH
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A reversible heat engine operates under two environments. In the first it draws 12000 kJ/s from a thermal source at 400°C and in the second environment, it draws 25000 kJ/s from a thermal source at 100°C. In both the operations, the engine rejects heat to a thermal sink at 20°C. Determine the operation in which the engine delivers more power.Long Answer 8 Marks May-2014 • PTU B-TECH
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Verify the statement “The efficiency of an irreversible engine is always less than the efficiency of reversible one operating between the same two thermal reservoirs”.Long Answer 8 Marks May-2014 • PTU B-TECH
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Dec 2016 Comment on the validity of the statement: All reversible engines operating between the same two thermal reservoirs have the same efficiency.
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Dec 2012 Comment on the validity of the statement: “All reversible engines operating between the same two thermal reservoirs have the same efficiency.”
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Air at 105 m/s and 1.25 kg/m^3 enters a gas turbine at the inlet area of 0.05 m^2. The air stream exits from the gas turbine at 135 m/s and 0.67 kg/m^3. During the flow process, the air loses 27 kJ/kg of heat and its specific enthalpy comes down by 145 kJ/kg. Determine: a) the mass flow rate of air through the turbine, b) the turbine exit area, c) the power developed by the turbine.Long Answer 8 Marks May-2014 • PTU B-TECH
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Define inequality of Clausius and entropy of a system. Show that for an irreversible process ds > dQ/T.Long Answer 8 Marks May-2014 • PTU B-TECH
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Dec 2016 Define entropy and show that for an irreversible process, dS > δQ/T.
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A heat engine is supplied with 278 kJ/s of heat at a constant fixed temperature of 283°C and the heat rejection takes place at 5°C. The following results were reported: a) 208 kJ/s of heat rejected b) 139 kJ/s of heat rejected c) 70 kJ/s of heat rejected. Classify which of the results report a reversible cycle, irreversible cycle or impossible cycle.Long Answer 8 Marks May-2014 • PTU B-TECH
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Show that the efficiency of a Brayton cycle depends only on the pressure ratio.Long Answer 4 Marks May-2014 • PTU B-TECH
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Dec 2008 Show that the efficiency of Otto cycle depends only on compression ratio.
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In an air standard Brayton cycle, air enters the compressor at 300 K and 1 bar. The pressure ratio is 8 and the maximum allowable temperature is 1300 K. Determine the temperature and pressure at each state of the cycle, compressor work, and turbine work per kg of air and cycle efficiency.Long Answer 4 Marks May-2014 • PTU B-TECH
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In a lifting machine an effort of 98.2 N raised a load of 1000 N and an effort of 498.2 N raised a load of 6000 N. Find the law of machine. Find what effort is required to lift a load of 10000 N? Find also the maximum mechanical advantage.Long Answer 4 Marks May-2014 • PTU B-TECH
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Explain differential pulley block arrangement with a neat sketch and find expression for velocity ratio.Long Answer 4 Marks May-2014 • PTU B-TECH
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Prove that the maximum stress induced in a body due to sudden applied load is twice the stress induced when the same load is applied gradually.Long Answer 4 Marks May-2014 • PTU B-TECH
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A weight W falls through 1 cm on a collar attached at the bottom of a vertical bar. The maximum instantaneous extension in the bar is 0.002 mm for a length of 3 m. The area of cross-section of the bar is 6 cm^2. Find the corresponding stress and the weight W. Take E = 200 GPa.Long Answer 4 Marks May-2014 • PTU B-TECH
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Dec 2010 An unknown weight falls 4 cm on to a collar rigidly attached to the lower end of a vertical bar 4 m long and 8 cm2 in section. If the maximum instantaneous extension is found to be 0.42 cm. Find the corresponding stress and the value of unknown weight E = 200 kN/mm2.
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Discuss working of a crank and slotted lever type of quick return mechanism with a neat sketch and explain its working.Long Answer 4 Marks May-2014 • PTU B-TECH
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Dec 2012 Sketch and describe the working of crank and slotted lever type quick return mechanism.
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Derive an expression for thermal efficiency of an Otto cycle and prove that for maximum work, compression ratio should be 1.25^(?)Long Answer 4 Marks May-2014 • PTU B-TECH
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01 Where can I find elements of mechanical engineering previous year question papers for Bachelor of Technology, 1st-2nd semester?
This page lists elements of mechanical engineering question papers uploaded for Punjab Technical University Bachelor of Technology, 1st-2nd semester, organized for subject-wise browsing where available.
02 Are these official Punjab Technical University question papers?
BRpaper is not the official website of Punjab Technical University. These papers are shared for reference and revision purposes only and are not official university material.
03 How can previous year elements of mechanical engineering papers help in exam preparation?
Reviewing past papers can help you understand how questions are typically framed, notice commonly repeated topics, and get a sense of the exam pattern before your own exam.
04 What kind of topics does elements of mechanical engineering usually cover?
The question papers here relate to the official elements of mechanical engineering syllabus set by the university for this course and semester.
05 Does this page include a elements of mechanical engineering question bank or solved answers?
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Yes, BRpaper organizes papers by university, course, stream, and semester, so you can browse other subjects within the same Punjab Technical University Bachelor of Technology.