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UPPSC AE Mechanical study materials
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UPPSC AE Mechanical practice questions

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Question 1Mechanical Engineering technical subject

In a simple Rankine cycle operating between fixed boiler and condenser pressures, which modification increases the cycle thermal efficiency without changing the turbine inlet pressure?

  1. Superheating the steam at the turbine inlet
  2. Reheating the steam after partial expansion
  3. Increasing the boiler feedwater temperature by regenerative feed heating Correct answer.
  4. Reducing the condenser pressure below atmospheric

Explanation

Bleeding steam to heat the feedwater raises the mean temperature of heat addition while keeping the boiler pressure fixed, so the cycle efficiency improves at the same turbine inlet pressure. Superheating and reheating also help, but they change the state at the turbine inlet, which the stem excludes. Lowering condenser pressure improves efficiency but is a pressure change, not the intended answer here.

Question 2Mechanical Engineering technical subject

The degree of reaction of an axial flow compressor stage is defined as the ratio of the static enthalpy rise in the rotor to which quantity?

  1. The stagnation enthalpy rise in the stage
  2. The static enthalpy rise in the stage Correct answer.
  3. The stagnation pressure rise in the stage
  4. The static pressure rise in the stage

Explanation

Degree of reaction compares the static enthalpy (or static pressure) rise across the rotor with the total static rise across the whole stage. A 50 percent reaction stage splits the static enthalpy rise equally between rotor and stator. Pressure ratios are not used directly because the definition is based on enthalpy rise.

Question 3Mechanical Engineering technical subject

A simply supported beam of span L carries a central point load W. What is the maximum bending moment?

  1. WL/8
  2. WL/2
  3. WL
  4. WL/4 Correct answer.

Explanation

For a simply supported beam with a central point load, each reaction equals W/2 and the maximum moment occurs at midspan, giving (W/2)(L/2) = WL/4. The value WL/8 applies to a uniformly distributed load, not a central point load.

Question 4Mechanical Engineering technical subject

In a two-stroke SI engine, the scavenging process occurs during which part of the piston travel?

  1. Only near top dead centre
  2. Near bottom dead centre Correct answer.
  3. Throughout the entire upward stroke
  4. Only during the middle of the downward stroke

Explanation

In a crankcase-scavenged two-stroke engine, the transfer and exhaust ports are uncovered by the piston near bottom dead centre, so fresh charge enters while burnt gases leave. This is why scavenging and the power stroke overlap in time. Ports are not open near top dead centre or during the whole stroke.

Question 5Mechanical Engineering technical subject

The main purpose of providing a volute casing in a centrifugal pump is to:

  1. Balance the axial thrust on the shaft
  2. Convert the kinetic energy of the leaving fluid into pressure energy Correct answer.
  3. Prevent recirculation at the impeller inlet
  4. Increase the impeller speed without cavitation

Explanation

The volute has a gradually increasing flow area that diffuses the high-velocity discharge from the impeller, converting kinetic energy into pressure energy. It does not drive the impeller or balance axial thrust. Inlet recirculation is controlled by the suction geometry, not the volute.

Question 6Mechanical Engineering technical subject

Which dimensionless number governs the relative importance of inertial forces to viscous forces in a pipe flow?

  1. Froude number
  2. Weber number
  3. Mach number
  4. Reynolds number Correct answer.

Explanation

The Reynolds number is the ratio of inertial to viscous forces and determines whether pipe flow is laminar or turbulent. Froude number relates inertia to gravity, Mach number relates flow speed to sound speed, and Weber number relates inertia to surface tension.

Question 7Mechanical Engineering technical subject

In a single plate clutch, the uniform pressure theory is applicable when the plate is:

  1. Made of sintered metal
  2. New and well bedded in Correct answer.
  3. Worn and running hot
  4. Operating above its rated torque

Explanation

Uniform pressure theory applies to a new clutch whose friction surfaces have not yet worn to conform, so contact pressure is assumed constant over the area. After bedding in, uniform wear theory is more appropriate because the lining wears until the product of pressure and radius is constant. Material type and overload do not decide which theory is used.

Question 8Mechanical Engineering technical subject

A spur gear pair has 20 and 40 teeth and a module of 4 mm. What is the standard centre distance?

  1. 120 mm Correct answer.
  2. 240 mm
  3. 160 mm
  4. 80 mm

Explanation

Pitch circle diameters are m times the tooth numbers, giving 80 mm and 160 mm. The standard centre distance is half the sum of the pitch circle diameters, that is (80 + 160)/2 = 120 mm. The other values come from using one diameter alone or adding diameters without halving.

Question 9Mechanical Engineering technical subject

A body is in complete static equilibrium under a general coplanar force system. Which set of conditions must hold?

  1. Sum of forces zero only
  2. Sum of forces zero and sum of moments about one point zero Correct answer.
  3. Sum of forces maximum and moment minimum
  4. Sum of moments about any one point zero only

Explanation

For coplanar equilibrium, the vector sum of all forces and the sum of moments about any single point must both vanish. Once these hold, the moment sum about every other point is automatically zero. Satisfying only one condition leaves a possible unbalanced translation or rotation.

Question 10Mechanical Engineering technical subject

In a slider-crank mechanism, the quick return action is obtained only when the mechanism is modified into which form?

  1. A double slider-crank
  2. A pantograph
  3. An offset slider-crank
  4. A Whitworth quick return mechanism Correct answer.

Explanation

The Whitworth (and crank and slotted lever) mechanism produces unequal forward and return times of the ram, giving quick return. An offset slider-crank has unequal stroke timing but is not the standard quick return arrangement. A double slider produces straight-line motion, and a pantograph copies paths.

Question 11Mechanical Engineering technical subject

A steel rod of length 1 m and cross-sectional area 100 mm² is subjected to an axial tensile load of 10 kN. Taking E = 200 GPa, the elongation is:

  1. 50 mm
  2. 0.05 mm
  3. 0.5 mm Correct answer.
  4. 5 mm

Explanation

Elongation equals PL/(AE). Here P = 10 000 N, L = 1 m, A = 100 × 10⁻⁶ m², and E = 200 × 10⁹ N/m², giving 10 000/(20 000 000) = 5 × 10⁻⁴ m, that is 0.5 mm. The other values differ by factors of ten from an arithmetic slip.

Question 12Mechanical Engineering technical subject

For a circular shaft of diameter d transmitting torque T, the maximum shear stress is given by:

  1. 32T/(πd³)
  2. 8T/(πd²)
  3. 16T/(πd³) Correct answer.
  4. T/(πd³)

Explanation

The polar section modulus of a solid circular shaft is πd³/16, so the maximum shear stress equals T divided by that modulus, giving 16T/(πd³). The expression 32T/(πd³) belongs to bending stress with the bending section modulus. The other forms lack the correct geometric factor.

Question 13Mechanical Engineering technical subject

A Carnot engine operates between 600 K and 300 K. Its thermal efficiency is:

  1. 75 percent
  2. 25 percent
  3. 50 percent Correct answer.
  4. 33 percent

Explanation

Carnot efficiency depends only on the absolute source and sink temperatures: 1 − T_L/T_H = 1 − 300/600 = 0.5, or 50 percent. Using Celsius temperatures or inverting the ratio gives the wrong figures. No real engine can exceed this value between the same reservoirs.

Question 14Mechanical Engineering technical subject

In a vapour compression refrigeration cycle, the function of the expansion device is to:

  1. Remove superheat from the condenser outlet
  2. Increase the refrigerant enthalpy before compression
  3. Reduce pressure and partially flash the refrigerant before the evaporator Correct answer.
  4. Compress the refrigerant isentropically

Explanation

The expansion valve or capillary throttles the liquid refrigerant from condenser pressure to evaporator pressure, causing partial flashing and a drop in temperature. The process is isenthalpic, not isentropic compression. Superheat removal is done in the condenser, and the expansion device does not raise enthalpy.

Question 15Mechanical Engineering technical subject

In a boiler, the device used to separate moisture from steam before it leaves the drum is called a:

  1. Steam separator or dryer Correct answer.
  2. Superheater
  3. Economiser
  4. Air preheater

Explanation

Steam separators or dryers use baffles or centrifugal action to remove entrained water droplets from steam leaving the boiler drum. Economisers heat feedwater, superheaters raise steam temperature, and air preheaters heat combustion air. These latter components do not remove moisture.

Question 16Mechanical Engineering technical subject

In a counterflow heat exchanger with equal heat capacity rates on both sides, the effectiveness for a very large number of transfer units approaches:

  1. 0.5
  2. 1.0 Correct answer.
  3. Infinity
  4. Zero

Explanation

When the two capacity rates are equal, effectiveness equals NTU/(1 + NTU) for counterflow, which tends to 1.0 as NTU becomes large. Physically this means the outlet of the hot stream approaches the inlet temperature of the cold stream. Effectiveness is bounded between 0 and 1 by definition.

Question 17Mechanical Engineering technical subject

Which mechanism of heat transfer does not require a material medium?

  1. Forced convection
  2. Conduction
  3. Free convection
  4. Radiation Correct answer.

Explanation

Thermal radiation propagates as electromagnetic waves and therefore travels through vacuum, as heat from the Sun reaches Earth. Conduction needs molecular contact, and both free and forced convection require a moving fluid. Hence only radiation works without a medium.

Question 18Mechanical Engineering technical subject

A flat plate of area 0.5 m² is pulled over a thin oil film of thickness 1 mm at 2 m/s. If the oil viscosity is 0.2 Pa·s, the force required is:

  1. 200 N Correct answer.
  2. 400 N
  3. 100 N
  4. 50 N

Explanation

For a thin film, shear stress equals viscosity times velocity gradient, τ = μV/t = 0.2 × 2/0.001 = 400 Pa. Multiplying by the plate area gives F = 400 × 0.5 = 200 N. Errors arise from omitting area or misplacing the thickness conversion.

Question 19Mechanical Engineering technical subject

In Bernoulli's equation applied along a streamline of an ideal fluid, which quantity remains constant?

  1. Velocity head alone
  2. The sum of pressure head, velocity head, and elevation head Correct answer.
  3. Static pressure alone
  4. The product of pressure and velocity

Explanation

For steady, incompressible, frictionless flow along a streamline, the total head p/ρg + V²/2g + z stays constant while individual terms may vary. Static pressure and velocity head change as the area changes. The product of pressure and velocity has no conservation significance here.

Question 20Mechanical Engineering technical subject

A Pelton wheel is best suited for which combination of head and discharge?

  1. Medium head and medium discharge
  2. High head and small discharge Correct answer.
  3. Low head and large discharge
  4. High discharge at any head

Explanation

Pelton wheels are impulse turbines driven by high-velocity jets, so they suit high heads with relatively small discharges. Low head and large discharge favour reaction turbines such as Kaplan. Francis turbines occupy the medium range.

Question 21Mechanical Engineering technical subject

The composition of a eutectoid plain carbon steel corresponds approximately to which carbon content?

  1. 2.0 percent
  2. 0.8 percent Correct answer.
  3. 4.3 percent
  4. 0.2 percent

Explanation

The eutectoid reaction in the iron-carbon system occurs near 0.8 percent carbon and about 723 °C, producing pearlite from austenite. The 0.2 percent composition is hypoeutectoid, 2.0 percent lies in the hypereutectoid range, and 4.3 percent is the eutectic point of cast iron.

Question 22Mechanical Engineering technical subject

In metal cutting, the tool signature 0-10-6-6-8-90-1 indicates a back rake angle of:

  1. 6 degrees
  2. 0 degrees Correct answer.
  3. 90 degrees
  4. 10 degrees

Explanation

The ASA tool signature lists back rake, side rake, end relief, side relief, end cutting edge angle, side cutting edge angle, and nose radius in that order. The first number, 0, is therefore the back rake angle. The 10 is side rake, and 90 is the side cutting edge angle.

Question 23Mechanical Engineering technical subject

Which welding process uses a non-consumable tungsten electrode with an inert shielding gas?

  1. Submerged arc welding
  2. Electroslag welding
  3. Tungsten inert gas welding Correct answer.
  4. Gas metal arc welding

Explanation

Tungsten inert gas welding, also called gas tungsten arc welding, uses a non-consumable tungsten electrode and argon or helium shielding. GMAW uses a consumable wire, submerged arc welding uses granular flux, and electroslag welding uses molten slag for resistance heating.

Question 24Mechanical Engineering technical subject

A cylindrical riser is to feed a steel casting. According to Chvorinov's rule, solidification time is proportional to which power of the volume-to-surface-area ratio?

  1. Square Correct answer.
  2. Cube
  3. Square root
  4. First power

Explanation

Chvorinov's rule states that solidification time equals a mould constant times (V/A)², so the ratio is squared. This is why a riser must have a larger V/A than the casting it feeds so it freezes later. Linear, cubic, and square-root forms do not match the rule.

Question 25Mechanical Engineering technical subject

In a vapour absorption refrigeration system, the compressor of the vapour compression cycle is replaced by which combination?

  1. An absorber, a pump, a generator, and a rectifier Correct answer.
  2. An evaporator and a condenser only
  3. A superheater and a regenerator
  4. A single expansion valve and a fan

Explanation

Absorption systems use an absorber, a liquid pump, a generator, and usually a rectifier to raise the refrigerant back to high pressure and purity, replacing mechanical compression. The pump handles liquid and needs little work. The evaporator and condenser are still present but do not replace the compressor function.

Question 26Mechanical Engineering technical subject

In a tensile test on a ductile mild steel specimen, the engineering stress at which the load-extension curve becomes horizontal before necking is known as the:

  1. Ultimate tensile strength Correct answer.
  2. Yield strength
  3. Proportional limit
  4. Breaking strength

Explanation

The maximum engineering stress on the curve is the ultimate tensile strength, occurring where the curve flattens as local necking begins. Beyond this point the load falls off until fracture. The proportional limit and yield strength lie much earlier on the curve.

Question 27Mechanical Engineering technical subject

A simply supported beam of span L carries a central point load W. The maximum bending moment in the beam is:

  1. WL
  2. WL/2
  3. WL/4 Correct answer.
  4. WL/8

Explanation

Reactions at each support are W/2, and the maximum moment occurs at mid-span where the lever arm is L/2. Multiplying gives (W/2)(L/2) = WL/4. For a uniformly distributed load the corresponding value would be WL/8.

Question 28Mechanical Engineering technical subject

Which crystal structure is exhibited by alpha-iron (ferrite) at room temperature?

  1. Body-centred cubic Correct answer.
  2. Face-centred cubic
  3. Close-packed hexagonal
  4. Simple cubic

Explanation

Ferrite, the room-temperature form of iron, has a body-centred cubic lattice with atoms at the corners and one at the body centre. On heating above about 912 degrees Celsius it transforms to face-centred cubic austenite.

Question 29Mechanical Engineering technical subject

In a four-stroke diesel engine, the fuel is injected:

  1. At the start of the suction stroke
  2. At the beginning of the power stroke after spark ignition
  3. Just before the end of the compression stroke Correct answer.
  4. During the exhaust stroke

Explanation

In a diesel engine the fuel must be injected near the end of compression so that the high air temperature causes self-ignition. Injection slightly before top dead centre allows time for atomisation and ignition delay. There is no spark plug in this cycle.

Question 30Mechanical Engineering technical subject

The unit of dynamic viscosity in the SI system is:

  1. m²/s
  2. N/m
  3. N·s/m² Correct answer.
  4. kg/m³

Explanation

Dynamic viscosity relates shear stress to velocity gradient, giving units of N·s/m², also called the pascal-second. The unit m²/s belongs to kinematic viscosity. N/m is a surface tension unit and kg/m³ is density.

Question 31Mechanical Engineering technical subject

In a reciprocating pump, the air vessel is fitted on the delivery side mainly to:

  1. Prevent cavitation at the suction valve
  2. Reduce the acceleration head and give a nearly constant discharge Correct answer.
  3. Increase the speed of the crank
  4. Increase the suction lift

Explanation

An air vessel stores energy during the acceleration phase of the piston and releases it during deceleration, smoothing the flow and reducing the acceleration head. This gives an almost uniform discharge and lowers frictional losses. It does not change the suction lift or crank speed.

Question 32Mechanical Engineering technical subject

In a single-point cutting tool, the angle between the tool flank face and the machined surface is called the:

  1. Wedge angle
  2. Cutting angle
  3. Rake angle
  4. Clearance angle Correct answer.

Explanation

The clearance angle is measured between the flank face and the newly machined surface, and it prevents rubbing. The rake angle is measured on the face where the chip flows. The wedge angle lies between the rake and clearance faces.

Question 33Mechanical Engineering technical subject

In a shell-and-tube heat exchanger, baffles are provided on the shell side primarily to:

  1. Increase the tube-side velocity
  2. Direct the shell-side fluid across the tubes and increase turbulence Correct answer.
  3. Reduce the pressure drop on the shell side
  4. Support the tube sheet against thermal expansion

Explanation

Baffles force the shell-side fluid to flow across the tube bundle rather than along it, raising turbulence and the shell-side heat transfer coefficient. A side effect is an increase, not a decrease, in shell-side pressure drop. They do not change tube-side velocity.

Question 34Mechanical Engineering technical subject

A gas undergoes an isothermal reversible expansion at temperature T. For an ideal gas, the change in internal energy is:

  1. Zero Correct answer.
  2. Equal to the work done by the gas
  3. Equal to the heat supplied divided by T
  4. Positive because the volume increases

Explanation

For an ideal gas, internal energy depends only on temperature. Since the temperature is constant in an isothermal process, the change in internal energy is zero, and the heat supplied equals the work done.

Question 35Mechanical Engineering technical subject

A shaft transmits 15 kW at 300 rpm. The torque transmitted by the shaft is approximately:

  1. 47.7 N·m
  2. 477 N·m Correct answer.
  3. 4 770 N·m
  4. 50 N·m

Explanation

Power equals torque times angular velocity, with angular velocity equal to 2πN/60. Here 2π×300/60 is about 31.4 rad/s, so torque is 15 000/31.4, approximately 477 N·m.

Question 36Mechanical Engineering technical subject

A thin cylindrical pressure vessel of diameter D and wall thickness t is subjected to internal pressure p. The hoop stress developed is:

  1. pD/t
  2. pD/(2t) Correct answer.
  3. 2pD/t
  4. pD/(4t)

Explanation

Force balance on a longitudinal section gives hoop stress as pD/(2t), which is twice the longitudinal stress. The longitudinal stress is pD/(4t). Thin-shell theory assumes t is small compared with D.

Question 37Mechanical Engineering technical subject

In a belt drive, the ratio of tensions on the tight and slack sides is given by T1/T2 = e^(μθ). The term θ represents the:

  1. Coefficient of friction between belt and pulley
  2. Angle of the V-groove in a flat belt pulley
  3. Angle of contact or lap in radians on the pulley being considered Correct answer.
  4. Total length of belt in contact with the smaller pulley only

Explanation

The belt friction equation uses θ as the angle of lap in radians over which the belt contacts the pulley. For an open belt drive the smaller pulley has the smaller lap and therefore governs the limiting tension ratio. μ is the coefficient of friction.

Question 38Mechanical Engineering technical subject

A gas turbine operates on a Brayton cycle between pressure limits of 1 bar and 9 bar. Taking the ratio of specific heats as 1.4, the ideal cycle efficiency is approximately:

  1. 36 %
  2. 50 % Correct answer.
  3. 64 %
  4. 44 %

Explanation

Brayton cycle efficiency equals 1 minus the reciprocal of the pressure ratio raised to (γ-1)/γ. Here the pressure ratio is 9 and its exponent 0.286 gives about 1.87, so efficiency is roughly 1 - 1/1.87, close to 50 percent.

Question 39Mechanical Engineering technical subject

In a journal bearing, the Sommerfeld number is a function of bearing dimensions, clearance, viscosity, speed and load. It is primarily used to:

  1. Calculate the shaft critical speed
  2. Characterise the operating regime and friction coefficient of the bearing Correct answer.
  3. Predict the fatigue life of the bearing material
  4. Determine the thermal conductivity of the lubricant

Explanation

The Sommerfeld number groups viscosity, speed, load and geometry into one dimensionless parameter that correlates with the friction coefficient and identifies the operating regime, from boundary to hydrodynamic lubrication. It does not predict fatigue life or critical speed.

Question 40Mechanical Engineering technical subject

In a bolted joint, the initial tension in the bolt is 20 kN and the external load shared by the bolt is 8 kN. If the joint stiffness ratio gives a load factor of 0.3, the total bolt load is:

  1. 22.4 kN Correct answer.
  2. 20 kN
  3. 8 kN
  4. 28 kN

Explanation

The total bolt load equals initial tension plus the fraction of external load taken by the bolt, that is 20 + 0.3×8 = 22.4 kN. The remainder of the external load relieves the clamped members.

Question 41Mechanical Engineering technical subject

A composite wall consists of two layers in series with thermal resistances of 0.2 K/W and 0.3 K/W. If the temperature difference across the wall is 100 K, the heat flow rate is:

  1. 500 W
  2. 200 W Correct answer.
  3. 333 W
  4. 50 W

Explanation

For layers in series the resistances add, giving a total of 0.5 K/W. Heat flow equals temperature difference divided by total resistance, that is 100/0.5 = 200 W.

Question 42Mechanical Engineering technical subject

In a reaction turbine, the degree of reaction is defined as the ratio of:

  1. Enthalpy drop in the rotor to the total stage enthalpy drop Correct answer.
  2. Blade velocity to the whirl velocity at inlet
  3. Rotor speed to the spouting velocity
  4. Static pressure drop to the velocity head

Explanation

Degree of reaction expresses how much of the stage enthalpy drop occurs in the moving blades compared with the whole stage. A fifty percent reaction turbine splits the drop equally between stator and rotor. The other ratios describe velocity diagrams, not reaction.

Question 43Mechanical Engineering technical subject

In a Kaplan turbine, the guide vanes are adjusted together with the runner blade angle. This feature is provided to:

  1. Reduce the weight of the runner
  2. Prevent cavitation at the draft tube
  3. Increase the head available at the runner
  4. Maintain high efficiency over a wide range of flows Correct answer.

Explanation

Kaplan turbines use double regulation, adjusting both guide vanes and runner blades so that the velocity triangles stay favourable at part load. This keeps efficiency high over a broad flow range, which is important for low-head, large-flow installations.

Question 44Mechanical Engineering technical subject

In a vapour compression refrigeration cycle using R-134a, subcooling the liquid leaving the condenser, with all other conditions unchanged, results in:

  1. An increase in refrigerating effect Correct answer.
  2. A decrease in compressor work only
  3. A decrease in refrigerating effect
  4. No change in the coefficient of performance

Explanation

Subcooling lowers the enthalpy of the liquid entering the expansion device, so more heat can be absorbed in the evaporator for the same compressor work. This increases the refrigerating effect and improves the coefficient of performance.

Question 45Mechanical Engineering technical subject

In a sand casting, a cylindrical riser of diameter D and height D is used. If a second geometrically similar riser has twice the diameter and height, the solidification time of the larger riser compared with the smaller one is:

  1. Two times
  2. Four times Correct answer.
  3. Unchanged
  4. Eight times

Explanation

Chvorinov's rule states that solidification time is proportional to the square of the volume-to-surface-area ratio. For a geometrically similar body, doubling all dimensions doubles this modulus, so solidification time increases by a factor of four.

Question 46Mechanical Engineering technical subject

In a rolling operation, the maximum possible reduction is limited by the roll radius and friction. The condition for the metal to be drawn into the rolls is that the:

  1. Roll radius exceeds the final thickness
  2. Angle of bite is less than or equal to the friction angle Correct answer.
  3. Roll speed exceeds the exit velocity of the strip
  4. Coefficient of friction is less than the draft ratio

Explanation

For the strip to enter the roll gap, the friction angle must equal or exceed the angle of bite, which is set by the draft and roll radius. This condition gives the well-known limiting draft of μ²R.

Question 47Mechanical Engineering technical subject

In a metal cutting operation, the specific cutting energy is found to decrease as the uncut chip thickness increases. This behaviour is mainly attributed to:

  1. Increase in the shear plane angle only
  2. The size effect, where the sharper tool edge and reduced work material strain hardening dominate at small feeds Correct answer.
  3. Reduction of the tool-chip contact length at small feeds
  4. Decrease in cutting temperature at large feeds

Explanation

At small uncut chip thickness the cutting edge radius is comparable to the chip thickness, so ploughing and severe strain gradients raise the specific energy. This size effect explains why specific cutting energy falls as feed increases.

Question 48Mechanical Engineering technical subject

A component made of steel is to be surface hardened while retaining a tough core. Which treatment is most appropriate?

  1. Case carburising followed by quenching and tempering Correct answer.
  2. Full annealing
  3. Stress relieving
  4. Normalising

Explanation

Carburising enriches the surface in carbon, so subsequent quenching hardens only the case while the low-carbon core remains tough. Annealing and normalising soften the whole section, and stress relieving does not increase hardness.

Question 49Mechanical Engineering technical subject

A simply supported beam of rectangular section is loaded by a central point load. If the depth of the section is doubled while the width and span remain the same, the maximum deflection becomes:

  1. One quarter of the original
  2. One eighth of the original Correct answer.
  3. One half of the original
  4. One sixteenth of the original

Explanation

The central deflection of a simply supported beam under a point load is proportional to 1/I. For a rectangular section, the second moment of area varies with the cube of the depth, so doubling depth raises I by eight and reduces deflection to one eighth.

Question 50Mechanical Engineering technical subject

In a two-stage reciprocating air compressor with perfect intercooling, the intermediate pressure that gives minimum total work is:

  1. The arithmetic mean of suction and delivery pressures
  2. Equal to the suction pressure
  3. The geometric mean of suction and delivery pressures Correct answer.
  4. Equal to the delivery pressure

Explanation

With perfect intercooling, total work is minimised when the pressure ratio is the same in both stages, which makes the intermediate pressure the geometric mean of the suction and delivery pressures. This also equalises the stage delivery temperatures.