Past Questions — 2010

Frederick Winslow Taylor (F.W. Taylor) is widely recognized as the 'Father of Scientific Management' and the 'Father of Industrial Engineering'. He pioneered the application of scientific methods to the analysis of work, focusing on improving economic efficiency and labor productivity. He introduced concepts such as time and motion studies, the differential piece-rate system, and the standardization of tools. Analysis of other options: - Newton: Sir Isaac Newton was a physicist and mathematician known for the laws of motion and universal gravitation, not industrial engineering. - Gnatt (Gantt): Henry Gantt was a contemporary of Taylor and developed the Gantt Chart for project management, but he is not considered the father of the entire field. - Jeck Gilberth (Frank and Lillian Gilbreth): The Gilbreths were pioneers in motion study and ergonomics, contributing significantly to the field, but Taylor's foundational work in scientific management precedes and encompasses the broader birth of Industrial Engineering.

Bending stress σ=M y /I, inversely proportional to section modulus (I/y).

Iron exhibits allotropy, meaning it exists in different crystal structures depending on the temperature. 1. Alpha-iron (α-Fe): This is the stable form of iron at room temperature (up to 912°C). It possesses a Body-Centered Cubic (BCC) structure. In this arrangement, there is one atom at each corner of the cube and one atom at the center of the cube. 2. Gamma-iron (γ-Fe): Also known as austenite, this form exists between 912°C and 1394°C and possesses a Face-Centered Cubic (FCC) structure. 3. Delta-iron (δ-Fe): This form exists from 1394°C up to the melting point (1538°C) and reverts to a Body-Centered Cubic (BCC) structure. Therefore, alpha iron is specifically characterized by a body-centered cubic lattice.

In the Theory of Machines, a kinematic pair is classified based on the type of contact between the two mating elements: 1. **Lower Pair**: When two elements have surface contact (area contact) while in motion, it is called a lower pair. Examples include sliding pairs (piston and cylinder), turning pairs (shaft in a bearing), and screw pairs. 2. **Higher Pair**: When two elements have point or line contact during motion, it is called a higher pair. Examples include gear teeth in mesh, cam and follower, or ball bearings. Analyzing the options: - Option (a) is incorrect because higher pairs involve point or line contact. - Option (b) is correct as surface contact is the defining characteristic of a lower pair. - Option (c) is incorrect because 'surface pair' is not a standard technical term used in kinematic classification. - Option (d) is incorrect because a rolling pair is a specific type of contact (often a higher pair if it's a ball/roller) and does not encompass all surface contact pairs.

A planer is a large machine tool used to produce flat surfaces. To specify the capacity or 'size' of a planer, one must define the maximum dimensions of the workpiece it can accommodate. This is determined by two primary factors: 1) The size of the table (specifically the length and width), which determines the maximum length and width of the workpiece that can be clamped and moved during the reciprocating stroke. 2) The height of the cross rail (or the distance between the table and the cross rail), which determines the maximum height of the workpiece that can be machined. While stroke length is a characteristic of the machine's operation, the overall 'size' specification of the machine as a piece of equipment is defined by the physical envelope it can handle, which is the table dimensions and the cross rail height.

In a centrifugal governor, the sleeve moves up or down based on the balance between the centrifugal force (generated by the rotating fly-balls) and the downward force (usually provided by a spring or the weight of the balls). 1. When the speed of the governor increases, the centrifugal force increases, pushing the sleeve upward. 2. When the speed decreases, the centrifugal force decreases, and the sleeve moves downward. 3. For the sleeve to be in a state of equilibrium at a specific speed (constant speed), the net force acting on the sleeve must be zero. According to Newton's First Law of Motion, if an object (the sleeve) is at rest or moving at a constant velocity (constant position in the case of a governor running at a steady state), the vector sum of all forces acting upon it must be zero. Therefore, for a governor running at a constant speed, the sleeve remains at a fixed position, meaning the upward centrifugal force is exactly balanced by the downward restoring force, resulting in a net force of zero.

Backlash is the amount of clearance between mating gear teeth on the line of action. It is necessary to prevent jamming due to thermal expansion, manufacturing tolerances, and lubrication requirements. 1. **Module (a):** The module determines the size of the gear teeth. Larger modules result in larger teeth, which typically require a larger absolute amount of backlash to accommodate manufacturing tolerances and ensure smooth operation without interference. 2. **Pitch Line Velocity (b):** As gears rotate at higher speeds, the teeth experience centrifugal forces and, more importantly, thermal expansion due to friction and heat generation. To prevent the teeth from jamming (binding) as they expand thermally at high pitch line velocities, a greater amount of backlash must be provided. 3. **Tooth Profile (c):** While the profile (e.g., involute) determines how the gears mesh, the 'required' amount of backlash is a functional design decision based on the physical size (module) and the operating conditions (velocity/temperature), rather than the shape of the curve itself. Therefore, since both the physical dimensions (module) and the operational heat/expansion factors (pitch line velocity) dictate the necessary clearance, the correct answer is both module and pitch line velocity.

Hooke's law linear stress-strain holds only up to limit of proportionality, beyond which deviation starts.

The shear stress ($ au$) induced in a circular shaft subjected to a torque ($T$) is governed by the torsion formula: $\tau = \frac{T \cdot r}{J}$, where $T$ is the applied torque, $r$ is the radial distance from the center of the shaft, and $J$ is the polar moment of inertia. From this formula, it is evident that the shear stress is directly proportional to the radius ($r$). Therefore: 1. At the center of the shaft ($r = 0$), the shear stress is zero. 2. As the distance from the center increases, the shear stress increases linearly. 3. At the outer surface or circumference ($r = R$), the shear stress reaches its maximum value. This linear distribution explains why option (c) is correct and options (a) and (b) are incorrect.

PERT (Program Evaluation and Review Technique) is a project management tool used primarily for projects where activity durations are uncertain. To account for this uncertainty, PERT uses a probabilistic approach involving three time estimates for each activity: 1. Optimistic Time (to): The minimum time required to complete an activity if everything goes perfectly. 2. Most Likely Time (tm): The most realistic time estimate, representing the duration that would occur most frequently if the activity were repeated many times. 3. Pessimistic Time (tp): The maximum time required if significant delays or obstacles occur. These three estimates are used to calculate the Expected Time (te) using the formula: te = (to + 4tm + tp) / 6. In contrast, CPM (Critical Path Method) typically uses a single-time (deterministic) estimate, making option 'a' incorrect. Options 'b' and 'd' are not standard practices in project management network analysis.

The Coriolis component of acceleration occurs when a point moves along a path that is itself rotating. Mathematically, it is expressed as 2vω, where 'v' is the velocity of the point relative to the rotating frame and 'ω' is the angular velocity of that frame. 1. In a Quick Return Mechanism (specifically the Crank and Slotted Lever mechanism used in shapers), the slider moves along the slotted lever. Since the slider has a velocity (v) relative to the lever and the lever itself is rotating (ω), a Coriolis acceleration component is generated. This is a classic textbook example of Coriolis acceleration in machine theory. 2. In a simple Four Bar Chain mechanism, the links are rigid; there is no point moving relative to a rotating link, so no Coriolis component exists. 3. In a standard Slider Crank mechanism, the piston moves relative to the cylinder (which is stationary) and the connecting rod rotates, but there is no point moving along a rotating link in the same manner as the slotted lever mechanism. Therefore, Coriolis acceleration is not encountered in the basic slider crank.

In the Theory of Machines, a 'mechanism' is defined as a combination of rigid or resistant bodies (links) so shaped and connected that they move with definite relative motion with respect to each other. To achieve a constrained motion that can transmit or transform motion (the primary purpose of a mechanism), a minimum of four links is required. For example, the simplest possible mechanism is the four-bar chain. A system with only two links (a binary joint) or three links (a triangular frame) is either a simple joint or a rigid structure (truss) and cannot provide the relative motion necessary to be classified as a mechanism. Therefore, a mechanism must consist of four or more links.

A Hooke's joint, also known as a Universal joint (U-joint), is used to connect two shafts whose axes intersect at a small angle. The mechanism consists of two Y-shaped components called 'forks' and a central cross-shaped piece called a 'spider' or 'cross'. Each fork is connected to one of the shafts, and the two forks are linked together by the cross. The cross allows the forks to rotate independently of each other while transmitting torque, enabling the joint to operate even as the angle between the shafts changes during rotation. Therefore, the joint consists of exactly two forks.

A double slider crank chain consists of four links: two sliders and two connecting links. In this mechanism, two sliders move along perpendicular guides. If we analyze the motion of any point on the link connecting the two sliders (the coupling link), its coordinates (x, y) can be expressed in terms of the positions of the sliders. Specifically, if the sliders move along the X and Y axes, the distance between them remains constant (the length of the link). This geometric constraint follows the equation x² + y² = L², where L is the length of the link. However, for any point other than the sliders themselves on that connecting link, the locus is an ellipse. This is a fundamental principle used in the construction of 'Elliptical Trammels,' a device specifically designed to draw a perfect ellipse using a double slider crank mechanism.

In the study of Strength of Materials, strain energy is the energy stored in a body due to deformation. 1. **Resilience**: This is the capacity of a material to absorb energy when it is deformed elastically and then, upon unloading, to have this energy recovered. It is the strain energy stored up to any point within the elastic limit. 2. **Proof Resilience**: This is the maximum energy that can be absorbed by a body per unit volume without permanent deformation. In other words, it is the strain energy stored when the material is stressed up to its elastic limit (or proportional limit). Since it is the 'maximum' energy stored within the elastic range, it is the correct answer. 3. **Toughness**: This is the total energy absorbed by a material up to the point of fracture. It includes both elastic and plastic deformation. While it is a 'maximum' energy, it refers to the energy until failure, not the stored energy typically associated with resilience. 4. **Impact Energy**: This refers to the energy absorbed by a material during a high-strain rate loading (like a Charpy or Izod test), which is a measure of toughness rather than a specific property of stored strain energy. Therefore, the maximum strain energy that can be stored (specifically within the elastic limit) is known as proof resilience.

To determine which quantity has no unit, we analyze the dimensions and definitions of each option: 1. **Kinematic Viscosity (a):** It is defined as the ratio of dynamic viscosity to density. Its SI unit is square meters per second (m²/s) or Stokes (St). It has dimensions [L²/T]. 2. **Surface Tension (b):** It is defined as the force per unit length acting on the surface of a liquid. Its SI unit is Newtons per meter (N/m). It has dimensions [MT⁻²]. 3. **Strain (c):** In the context of Strength of Materials, strain is defined as the ratio of the change in dimension (e.g., change in length $\Delta L$) to the original dimension (e.g., original length $L$). Since it is a ratio of two identical physical quantities (length/length), the units cancel out, making it a dimensionless quantity with no unit. 4. **Elasticity (d):** Elasticity (specifically the Modulus of Elasticity) is the ratio of stress to strain. Since stress has units of pressure (N/m² or Pascals) and strain is dimensionless, the unit of elasticity is the Pascal (Pa). It has dimensions [ML⁻¹T⁻²]. Therefore, Strain is the only quantity among the options that is dimensionless and has no unit.

The correct answer is buttress threads. Here is the detailed technical reasoning: 1. **Buttress Threads**: These are specifically designed for applications where the force (and thus the stress) is applied in only one direction. They have one face perpendicular (or nearly perpendicular) to the axis of the screw and the other face sloping. This design allows them to withstand very high axial loads in one direction while providing high efficiency, making them ideal for components like artillery breech blocks or screw jacks where the load is unidirectional. 2. **Square Threads**: These are used for power transmission because they have the highest efficiency (no radial pressure). However, they are designed to handle loads in both directions and are difficult to manufacture. 3. **Acme Threads**: These are a modification of square threads with a 29° angle. They are stronger and easier to manufacture than square threads and are used in lead screws of lathes. Like square threads, they are designed for bidirectional loads. 4. **Metric Threads**: These are standard V-threads (60° angle) primarily used for fastening purposes. They are not optimized for high-power transmission in a single direction. Therefore, for applications where stresses are encountered in one direction only, the buttress thread is the most efficient and appropriate choice.

White cast iron is characterized by the absence of graphite. In this material, the carbon is chemically combined with iron to form a hard, brittle intermetallic compound called iron carbide, also known as cementite (Fe3C). This occurs due to rapid cooling or a low silicon content, which prevents the carbon from precipitating as graphite. Because the surface of the fractured metal appears white (due to the presence of cementite and pearlite) rather than grey (due to graphite), it is termed 'white cast iron'. Analysis of other options: - a. Free carbon: This is a general term and not a specific metallurgical phase in cast iron. - b. Graphite: This is the form carbon takes in 'Grey Cast Iron'. - d. White carbon: This is not a standard metallurgical term for carbon in cast iron.

High Speed Steel (HSS) is an alloy steel specifically designed to maintain its hardness and cutting edge even at elevated temperatures generated during high-speed machining. Tungsten (W) is a primary alloying element in HSS. It forms hard, stable carbides (such as WC) that resist softening at high temperatures. This property is known as 'red hardness' or 'hot hardness.' While other elements like Chromium provide wear resistance and corrosion resistance, and Vanadium improves grain refinement and wear resistance, Tungsten is specifically credited with providing the hot hardness necessary for the tool to operate at high speeds without losing its temper. - Option b (toughness) is generally provided by the balance of carbon and alloying elements, but tungsten actually tends to decrease toughness if present in excess. - Option c (wear resistance) is provided by various carbides, including those formed by Vanadium and Chromium. - Option d (cold hardness) is a general property of hardened steels, not the specific purpose of adding Tungsten in HSS.

A helical gear is essentially a spur gear with teeth that are cut at an angle (the helix angle) relative to the axis of the gear. When you take a transverse section (a cross-section perpendicular to the axis of the gear), the curvature of the teeth and the profile of the gear appear exactly as they would in a spur gear. In a spur gear, the teeth are parallel to the axis, so any section perpendicular to the axis is identical to the gear's basic profile. Therefore, the transverse section of a helical gear is identical to that of a spur gear. Comparison with other options: - Bevel gears have conical shapes used for intersecting shafts, so their sections are not identical to helical transverse sections. - Worm gears consist of a worm (screw) and a worm wheel, which have entirely different geometries and tooth profiles compared to the transverse section of a helical gear.

To solve this question, we must analyze the casting methods mentioned in the options relative to the properties of ferrous alloys (such as steel and cast iron). 1. **Ferrous Alloys Characteristics**: Ferrous alloys have very high melting points (e.g., Steel melts around 1370°C to 1540°C). 2. **Die Casting (Options a, b, and c)**: Die casting involves forcing molten metal into a reusable metal mold (die) under high pressure. This process is primarily used for non-ferrous metals with lower melting points, such as Zinc, Aluminum, and Magnesium. 3. **Hot Chamber Machine (Option a)**: In this process, the melting pot is integrated into the machine. It is used for metals with low melting points (like Zinc) because high-melting-point metals would melt and destroy the pump and valves of the machine. 4. **Cold Chamber Machine (Option b)**: Here, the metal is melted in a separate furnace and poured into the chamber. While it can handle slightly higher temperatures than hot chamber machines (e.g., Aluminum), it is still not suitable for the extreme temperatures of ferrous alloys, as the molten steel would cause rapid thermal fatigue and erosion of the metal dies. 5. **Conclusion**: Ferrous alloys are typically cast using **Sand Casting**, **Investment Casting**, or **Centrifugal Casting**, where the molds can withstand the extreme heat. Since none of the die casting options (hot chamber, cold chamber, or general die casting) are suitable for standard ferrous alloy casting, the correct answer is 'none of them'.

In metal cutting using a single point tool, tool wear is generally categorized into two main types: Crater Wear and Flank Wear. 1. **Crater Wear**: This occurs on the rake face (the top surface of the tool) where the chip slides over the tool. It is caused by the high temperature and chemical diffusion between the tool material and the chip. This wear forms a concave 'crater' or depression on the face of the tool, typically just behind the cutting edge. 2. **Flank Wear**: This occurs on the flank face (the side of the tool that rubs against the finished surface of the workpiece). It is primarily caused by abrasion. Analyzing the options: - (a) Flank: This is where flank wear occurs, not crater wear. - (b) Side rake: While the rake face is involved, 'face' is the standard terminology for the surface where the crater forms. - (c) Face: Correct. The rake face is the specific area where the chip flows and where crater wear develops. - (d) Tip: While the tip is the point of contact, the crater extends back along the face, not just at the tip.

In a milling machine, the cutting tool (specifically the milling cutter) is mounted on a shaft called the arbor. The arbor is a precision-ground shaft that holds the cutter and is driven by the machine's spindle to provide the necessary rotational motion for material removal. Breakdown of options: - a. Tool holder: While general tools are held by holders, in the specific context of milling (especially horizontal milling), the primary mounting shaft is the arbor. - b. Arbor: Correct. It is the specific component designed to hold and rotate the milling cutter. - c. Spindle: The spindle is the main rotating shaft of the machine. While the arbor is inserted into or driven by the spindle, the tool itself is mounted on the arbor. - d. Column: The column is the main vertical structural support of the milling machine and does not hold the cutting tool.

In materials science and strength of materials, 'fatigue' refers to the progressive and localized structural damage that occurs when a material is subjected to cyclic loading. The key characteristic of fatigue is that failure (or yielding/fracture) occurs at a stress level significantly lower than the ultimate tensile strength or the yield strength measured under static (monotonic) loading. This is because cyclic stresses cause microscopic cracks to initiate and propagate over time, weakening the material's internal structure. Therefore, the effective stress level at which a material fails under fatigue loading is lower than the yield point observed during a standard static load test. Option (a) is incorrect because fatigue specifically reduces the load-bearing capacity. Option (b) is incorrect because cyclic loading never increases the strength of a material relative to its static yield point.

In arc welding, an electric arc is established between the electrode and the workpiece. The process begins when the electrode touches the workpiece, creating a short circuit. As the electrode is slightly withdrawn, the air gap is ionized. The continuous flow of electric current through this ionized gas (plasma) maintains the arc, which generates the intense heat required to melt the base metal and the filler electrode. While voltage is necessary to initiate the arc (open-circuit voltage) and electrical energy is the overall power source, it is specifically the flow of current (amperage) that sustains the arc and determines the heat input. Contact resistance is a factor during the initial strike but does not 'create' or maintain the arc itself.