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UPSC Mechanical Engineering — Previous Year Questions

Every question from Mechanical Engineering papers in UPSC Civil Services Mains (2021–2026), organised by year. 96 questions in total, each with directive-word analysis, model answer points, and a full evaluation rubric.

96Questions
6Years covered

2026 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2026

Paper I

  1. Q1 (a) A uniform beam has a mass of 50 kg per metre length. Compute the reactions at the support O. The force loads shown… 50 marks
  2. Q2 (a) What is heat treatment ? What is its purpose ? Explain different heat treatment processes with the help of common… 50 marks
  3. Q3 (a) (i) The acceleration of a particle along a straight line is defined by a = (2t – 9) m/s², where t is in seconds. At… 50 marks
  4. Q4 (a) A simple beam is loaded as shown in the figure. Using the double-integration method, determine the following : (i)… 50 marks
  5. Q5 (a) A cylindrical workpiece of 60 mm diameter is turned down to 50 mm over a length of 120 mm on a CNC lathe with… 50 marks
  6. Q6 (a) A strip of width 250 mm is reduced from 30 mm to 20 mm thickness in a rolling mill of roll radius 400 mm… 50 marks
  7. Q7 (a) (i) In an orthogonal cutting operation, the following data are obtained : Cutting force F_c = 1500 N Thrust force… 50 marks
  8. Q8 (a) A shaft of nominal size 60 mm is to be fitted into a hole. The tolerances are : Hole tolerance – 0·030 mm Shaft… 50 marks

Paper II

  1. Q1 (a) A piston-cylinder contains 2 kg of argon at T₁ = 300 K and V₁ = 1 m³ (state 1). Argon is heated by an electric… 50 marks
  2. Q2 (a) (i) During a heat transfer process, the entropy change of incompressible substances, such as water, can be… 50 marks
  3. Q3 (a) Steam at 40 °C is condensed in a power plant using cooling water available at 12 °C. The flow rate of steam is 0·15… 50 marks
  4. Q4 (a) (i) What does the NTU of a heat exchanger represent? Is a heat exchanger with a very large NTU necessarily a good… 50 marks
  5. Q5 (a) The air-fuel ratio of an SI engine varies under different operating conditions. Write the air-fuel ratio… 50 marks
  6. Q6 (a) In an Otto cycle, the pressure and temperature at the beginning of compression are 1 bar and 47 °C, respectively… 50 marks
  7. Q7 (a) In a cogeneration plant, the net power output is 6 MW and the heating load is 1·5 MW. Steam is generated at 40 bar… 50 marks
  8. Q8 (a) An air-conditioned space is maintained at 25 °C DBT and 50% RH. The outside conditions are 40 °C DBT and 27 °C WBT… 50 marks

2025 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2025

Paper I

  1. Q1 (a) A gripper is shown in the figure. A horizontal force F = 50 N is applied to the handle of the lever at E. The mean… 50 marks
  2. Q2 (a) (i) A cylinder C weighing 1000 N is supported by two cylinders A and B weighing 500 N each as shown in the figure… 50 marks
  3. Q3 (a) (i) The recoil mechanism of a gun consists of a critically damped spring-damper system. The maximum permissible… 50 marks
  4. Q4 (a) A car is moving in a straight line with a velocity of v = (0·6t² + 2t) m/s for a short duration, where t is in… 50 marks
  5. Q5 (a) A low carbon steel stock of thickness 25 mm is to be rolled in two stages. In the first stage, the reduction is to… 50 marks
  6. Q6 (a) (i) If the power source characteristic in a Metal Inert Arc welding process is V_P = 38 - I/60, and the arc… 50 marks
  7. Q7 (a) HSS cutting tool with 9° rake angle, the following data were observed in an orthogonal machining process of medium… 50 marks
  8. Q8 (a) What are the various computer languages used for NC machines? Explain the merits and limitations of each language… 50 marks

Paper II

  1. Q1 (a) A lump of ice with a mass of 1·5 kg at an initial temperature of 260 K melts at the pressure of 1 bar as a result… 50 marks
  2. Q2 (a) (i) A reversible power cycle engine is used to drive a reversible heat pump. The power cycle takes in Q₁ heat units… 50 marks
  3. Q3 (a) A long cylindrical rod of radius 10 cm consists of a nuclear reacting material (k = 0·5 W/m-K) generating 24000… 50 marks
  4. Q4 (a) A shell and tube type condenser is employed in a steam power plant to handle 35000 kg/h of dry and saturated steam… 50 marks
  5. Q5 (a) With the help of P-θ (pressure-crank angle) diagram, compare the knock in SI and CI engines. Explain that "the… 50 marks
  6. Q6 (a) A single-cylinder, two-stroke, high-speed diesel engine working on 'dual cycle' has a compression ratio of 15 : 1… 50 marks
  7. Q7 (a) A two-stage turbine receives steam at 50 bar and 350 °C. At 1·5 bar, the high-pressure stage exhausts and 12000 kg… 50 marks
  8. Q8 (a) The following data refers to a single-stage vapour compression refrigeration system : Refrigerant = R134a Condenser… 50 marks

2024 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2024

Paper I

  1. Q1 (a) A rod of length 2 m and weight 450 N rests on ground at one end. The other end is supported by a cord through which… 50 marks
  2. Q2 (a) Bodies A, B and C of weights 100 N, 200 N and 150 N, respectively are connected as shown. If released from rest… 50 marks
  3. Q3 (a) Show the loading on the beams corresponding to the bending moment diagrams shown below. The beams are simply… 50 marks
  4. Q4 (a) A governor of Hartnell type has each ball of weight 20 N and the lengths of vertical and horizontal arms of the… 50 marks
  5. Q5 (a) A cutting tool is used to machine alloy steel at cutting speed of 40 m/min. Considering the values of constants c… 50 marks
  6. Q6 (a) A perfectly plastic material having yield strength of 300 MPa is subjected to extrusion at 400 °C. The extrusion… 50 marks
  7. Q7 (a) An orthogonal cutting of metal is performed using cutting speed of 120 m/min, tool rake angle 5° and width of cut 5… 50 marks
  8. Q8 (a) Explain the principle of electric discharge machining (EDM) using suitable diagram. Describe the effect of process… 50 marks

Paper II

  1. Q1 (a) A 2 gm quantity of air undergoes the following sequence of quasi-static processes in a piston-cylinder arrangement… 50 marks
  2. Q2 (a) Air flows through a 5 cm diameter pipe. Measurements indicate that at the inlet to the pipe the velocity is 70 m/s… 50 marks
  3. Q3 (a) A shell and tube heat exchanger used in a thermal power plant is designed to condense 500 kg/s of saturated steam… 50 marks
  4. Q4 (a) A convergent-divergent nozzle is designed to expand air from a chamber in which the pressure is 800 kPa and… 50 marks
  5. Q5 (a) Explain the functions of three types of superheaters used in power boilers. Sketch the heat addition process in… 50 marks
  6. Q6 (a) A four-cylinder gasoline engine has a bore of 75 mm and a stroke length of 100 mm. It is operated at 3000 rpm and… 50 marks
  7. Q7 (a) In a cooling tower used in a thermal power plant, 26,000 kg/s of air enters at DBT = 20°C and relative humidity at… 50 marks
  8. Q8 (a) A cogenerating steam power plant operates with a boiler output of 25 kg/s steam at 7 MPa, 500°C. The condenser… 50 marks

2023 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2023

Paper I

  1. Q1 (a) A heavy carriage wheel of weight W, and radius r is to be dragged over an obstacle of height h by a horizontal… 50 marks
  2. Q2 (a) In Figure 2(a), AB is a rigid bar, CE is a steel rod of 20 mm diameter and DF is a copper rod of 20 mm diameter. If… 50 marks
  3. Q3 (a) The coefficient of friction for all contacting surfaces in Figure 3(a) is 0·2. Does the 25 kg force move the block… 50 marks
  4. Q4 (a) Two involute gears in mesh have pressure angle of 20° and module of 6 mm. The number of teeth on pinion is 28 and… 50 marks
  5. Q5 (a) In an electrochemical machining process of an iron surface using sodium chloride solution as electrolyte, following… 50 marks
  6. Q6 (a) Following data were observed while machining two different work materials X and Y using a centre lathe machine: If… 50 marks
  7. Q7 (a) (i) A tube is to be drawn as per the dimensions given in the following Figure 7(a)(i) showing die, plug and tube… 50 marks
  8. Q8 (a) The following data represents the results of inspecting 50 units/day of personal computers produced by two… 50 marks

Paper II

  1. Q1 (a) A 50 kg block of iron at 500 K is placed into open atmosphere which is at a temperature of 285 K. The iron block… 50 marks
  2. Q2 (a) A 15 m high cylinder with a cross-sectional area of 0.6 m² contains 3 m³ of liquid water at 25 °C on the top of a… 50 marks
  3. Q3 (a) Heat is generated in a stainless steel plate (thermal conductivity = 22 W/m-K) of thickness 1 cm, at a uniform rate… 50 marks
  4. Q4 (a) Considering an ideal, isentropic gas flow through a nozzle, show that choking will occur at Mach number (M) = 1… 50 marks
  5. Q5 (a) Show in the form of a table, how the increase in the following variables affects (increase or decrease) the… 50 marks
  6. Q6 (a) The power output of a six-cylinder, four-stroke CI engine is absorbed by a hydraulic dynamometer for which the law… 50 marks
  7. Q7 (a) A convergent-divergent nozzle receives steam at 5 bar, 250 °C and expands it isentropically into a space at 1 bar… 50 marks
  8. Q8 (a) An SI engine working on the Otto cycle has cylinder bore of 210 mm and stroke length of 240 mm. The clearance… 50 marks

2022 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2022

Paper I

  1. Q1 (a) A slider-crank mechanism with crank radius 60 mm and connecting rod length 240 mm is shown in Figure 1(a). The… 50 marks
  2. Q2 (a) A 20 mm diameter shaft is subjected to a torque of 80 Nm and a downward bending moment of 100 Nm at the centre… 50 marks
  3. Q3 (a) A thin cylinder of diameter 200 mm and length 1000 mm is subjected to an internal pressure of 10 MPa. The allowable… 50 marks
  4. Q4 (a) An automobile weighing 15 kN is moving at a speed of 100 km per hour. The dynamic coefficient of friction between… 50 marks
  5. Q5 (a) An HSS drill during its life can drill 150 through holes in a 10 mm thick brass plate at a drill speed of 400 rpm… 50 marks
  6. Q6 (a) During turning of a steel rod of 100 mm diameter, at a speed of 600 rpm, feed of 0·32 mm/rev and 3 mm depth of cut… 50 marks
  7. Q7 (a) A firm has identified four operations, which are to be conducted in succession for an order to be processed. The… 50 marks
  8. Q8 (a) (i) Discuss the mechanism of material removal in ultrasonic machining. (10 marks) (ii) What are the different… 50 marks

Paper II

  1. Q1 (a) Consider the system shown in Fig. 1(a). The two chambers initially have equal volumes of 28 litres and contain air… 50 marks
  2. Q2 (a) 10 g of water at 20 °C is converted into ice at –10 °C at constant atmospheric pressure. Assuming the specific heat… 50 marks
  3. Q3 (a) (i) How do the specific work output and efficiency vary with pressure ratio in a gas turbine? (ii) Prove that the… 50 marks
  4. Q4 (a) A single-stage impulse turbine rotor has a mean blade ring diameter of 500 mm and rotates at a speed of 10000… 50 marks
  5. Q5 (a) Can alcohols be used as fuel in IC engine? Explain with advantages and disadvantages. (10 marks) (b) A water-filled… 50 marks
  6. Q6 (a) A four-cylinder diesel engine with swept volume of 0·98 litre is tested on a performance bed. The engine running at… 50 marks
  7. Q7 (a) (i) Briefly discuss HC, CO and NOₓ emission formation in SI engine. Explain the dependence of these emissions on… 50 marks
  8. Q8 (a) A VCR cycle refrigerator driven by a 60 kW compressor has a COP of 6·0. The enthalpies of saturated liquid and… 50 marks

2021 Mains

16 questions · 800 marks

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Paper I 8 Qs · 400 marksPaper II 8 Qs · 400 marks
All 16 questions from 2021

Paper I

  1. Q1 (a) What is the supporting force system at A for the cantilever beam shown in the figure ? Neglect the weight of the… 50 marks
  2. Q2 (a) In a slider-crank mechanism, the lengths of the crank and connecting rod are 150 mm and 600 mm respectively. Locate… 50 marks
  3. Q3 (a) What is the purpose of tempering of hardened steel? Explain the principle of tempering using suitable schematics… 50 marks
  4. Q4 (a) Find out the value of atomic packing factor for the FCC crystal structure. Calculate the radius of an iridium (Ir)… 50 marks
  5. Q5 (a) TIG welding of two sheets of 5 mm thickness is performed using welding current (I) of 200 A and arc voltage (V) of… 50 marks
  6. Q6 (a) Five jobs A, B, C, D and E need to be processed on a machine. Processing time (in days) and due date (from now) are… 50 marks
  7. Q7 A car servicing company is interested in reducing the waiting time for its customers. They select four customers… 50 marks
  8. Q8 The frontal working area of the electrode is 2000 mm² in a certain ECM operation in which the applied current = 1800… 50 marks

Paper II

  1. Q1 (a) Discuss briefly the functional differences between a fan, a blower and a compressor. (10 marks) (b) Prove that… 50 marks
  2. Q2 (a)(i) 3 kg of air is compressed in a reversible steady flow polytropic process from 100 kPa, 40°C to 1000 kPa. During… 50 marks
  3. Q3 (a)(i) Show that the effective conductance, (A_1F̄₁₂) for two black, parallel plates of equal area connected by… 50 marks
  4. Q4 (a) Two walls A and B are maintained at temperatures T_A and T_B, respectively. One end of a metal rod of length l is… 50 marks
  5. Q5 (a) What do you understand by the term EGR? Explain how EGR reduces NOₓ emission in CI engines. (10 marks) (b) The flue… 50 marks
  6. Q6 (a) (i) How does the mixture combustion in the combustion chamber of a C.I. engine differ from that of an S.I. engine?… 50 marks
  7. Q7 (a) (i) A single stage impulse steam turbine rotor has a diameter of 1·2 m and runs at 3000 rpm. The nozzle angle is… 50 marks
  8. Q8 (a) An ammonia vapour compression refrigeration system works between temperature limits of −6·7°C and 26·7°C. The… 50 marks

How Mechanical Engineering answers are marked

The shape the examiner expects, what earns the marks and the traps that lose them: the same card our rubrics for this subject are written from.

Answer skeleton

  1. Given
  2. Assumptions
  3. Governing equation
  4. Solve and interpret

What earns the marks

  • Draw the schematic and mark every state
  • State assumptions before applying the law
  • Check dimensional consistency
  • Interpret efficiency or result physically

What earns the extra mark

  • Labelled cycle diagram such as T-s or p-V

Traps that cost marks

  • Plugging numbers with no governing equation
  • Unmarked states
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