Mechanical Engineering Technical Questions

The angular velocity (in rad / s) of a body rotating at N revolutions per minute is

2πN/60

What is a process flow diagram?

A Process Flow Diagram is a user friendly, simplified sketch which illustrates general plant streams, major equipments and key central loops and shows the relationship between major components in the system. By using symbols to identify instruments and vessels it describes the primary flow course. They also provide e detail of mass/energy balance data along with stream composition and physical properties, however do not show minor components.

Explain the difference between pipe and a tube.

A pipe is measured based on its inner diameter (ID) whereas a tube is measured based on the outer diameter (OD). Other than the dimensions there is no major difference between the two.

Explain why re-heater is used in gas turbine

The advantage of reheater is that it significantly increases the thrust; which is a prime reason for its use in gas turbines.

Briefly explain the advantages of Cycloidal and Involute gears?

The advantages of the Cycloidal gears are as follows: > Having a wider flank as compared to Involute gears they are considered to have more strength and hence can withstand further load and stress. > The contact in case of cycloidal gears is between the concave surface and the convex flank. This results in less wear and tear. > No interference occurs in these types of gears. The advantages of Involute gears are as follows: > The primary advantage of involute gears is that it allows the changing of the centre distance of a pair without changing the velocity ratio. > The pressure angle remains constant from start to end teeth, this results in less wear and smooth running of the gears. > The involute gears are easier to manufacture as they can be generated in a single curve ( the face and flank ).

Why should a chain drive be used over a belt or rope driven drive? State pro`s and con`s?

The advantages of using a chain drives are: > In a chain drive no slip occurrence takes place. > The chains take less space as compared to rope or belts as they are made of metal and offer much strength. > The chain drives can be used at both short and long ranges and they offer a high level of transmission efficiency. > Chain drives can transmit more load and power as compared to belts. > A very high speed ratio can be maintained in one step of chain drives. Some of the cons of using a chain drive are: > The cost of producing chain drives is higher as compared to that of belts. > The chain drives must be serviced and maintained at regular intervals and henceforth their cost of ownership is high comparatively.

The moment of inertia of a square of side a about its diagonal is

(a^4)/12

Explain the types of sensors.

(i) Temperature Sensor- This device collects information about the temperature from a source and converts it to a form which is understandable by another device or person. Glass thermometer is the best example where mercury acts as the temperature sensor. (ii) IR Sensors- This device detects and/or emits infrared radiation to sense a particular phase in the environment. Mostly thermal radiation is emitted by all the objects in the infrared spectrum. This type of radiation is not visible to the human eye but the infrared sensor detects it. (iii) UV Sensors- These sensors measure the intensity of the ultraviolet radiation. This form of electromagnetic radiation has wavelengths which are longer than x-rays yet shorter than visible radiation. UV sensors can discover the exposure of environment to ultraviolet radiation. (iV) Touch Sensor- A touch sensor acts as a variable resistor based on the location where it is sensed. Proximity Sensor- A proximity sensor detects the presence of objects that are placed in close proximity without any point of contact.

State Newton's three laws of Motion.

- The law of inertia: Every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it. - Acceleration is produced when a force acts on a mass. The greater the mass (of the object being accelerated) the greater the amount of force needed (to accelerate the object). Force=Mass times acceleration. - For every action there is an equal and opposite reaction.

How many degrees of freedom did a four bar linkage posses?

1

One unit of BTU is how many Joules?

1 BTU=1055.06 Joules

5 factors to consider for wires

1. ensure size does not cause wires to overheat and start a fire. 2. it will have sufficient mechanical strength under ordinary strains. 3. it will not be so large it exceeds economical installation. 4. carfies enough voltage without a drop or loss. 5. cost of energy lost (I^2×R) due to voltage overcoming resistance will not be excessive.

A differential pulley block has larger and smaller diameters of 100 mm and 80 mm respectively. Its velocity ratio is

10

Calculate the correct drill size to be used to drill a hole for a ½ in. - 13 UNC thread.

11/26 inc. .43 inc. 0.43 inc. 0.43 11/26

Calculate the correct drill size to be used to drill a hole for an M 42 x 4.5 mm thread.

37.5 mm 37.5

What is meant by gear ratio?

A gear ratio is a direct measure of ratio of the rotational speeds of two or more interlocking gears.

What is mechanism?

A mechanism is an assembly of different parts which perform a complete motion and is often part of a machine.

Which instrument measures speed in a car?

A speedometer helps measure the speed in the car.

Define The Term Stability Of A Feed Back Control System ?

A system is said to be stable if the output of a system after fluctuations, variations or oscillations, settles at a reasonable value for any change in input.

What is Hess law?

According to the Hess law the energy transfer is simply independent of the way being followed. If the reactant and the product of the whole process are the same then same amount of energy will be dissipated or absorbed.

What are the advantage and disadvantage of using LPG in a car?

Advantages: The high octane rate enables it to blend better with air and to burn completely, generating less carbon. With less carbon buildup, spark plugs often last longer and oil changes are needed less frequently. Since it burns in the gaseous phase, it results in less corrosion and engine wear. In case of a spill, LPG evaporates quickly. Disadvantages The LPG requires servicing at approximately once a year. Since complete combustion occurs, more heat is liberated which is not advised for a long journey as the engine will get over heated. Installation of LPG is rather difficult.

What states the second law of Thermodynamics?

All the heat entering in a system cannot be transformed to work

The hammer most frequently used by machinists is known as the______________.

Ball peen hammer

What is a bearing? What are the different types of bearings?

Bearing is a device that helps smoother movement with minimal friction which in turn helps enhances efficiency and speed. Considering two types of loading, radial and thrust, there are different types of bearings which help handle these loads. The basic difference in the types of loads is essentially due to their ability to handle weight and different kinds of loads for various applications. Different types of bearings are: -Ball bearing -Roller bearing-Ball Thrust bearing -Roller thrust bearing -Tapered roller bearing -Magnetic bearings -Giant Roller Bearing

What are Bevel Gears and what are its types?

Bevel gears are the type of gears in which the two shafts happen to intersect. The gear faces which are tooth bearing are conical in shape. They are generally mounted on shafts which are 90 degrees apart but they can be made to work at other angles as well. The bevel gears are classified into the following types on the basis of pitch surfaces and shaft angles: > Mitre Gears: These types of gears are similar to each other ie. they have the same pitch angles and contain the same number of teeth. The shaft axes intersect at 90 degrees angle. > Angular bevel gears: When two bevel gears connect at any angle apart from 90 degrees. > Crown bevel gears: When the two shaft axes intersect at an angle greater than 90 and one of the bevel gears have a pitch angle of 90 degrees they are known as crown bevel gears. > Internal bevel gears: In these type of gears the teeth on the gears is cut on the inside area of the pitch cone.

The size of a hammer is usually determined by the:

Weight of its head

Types of wrench?

Box-end Allen or hexagonal Sockets

What are the different types of brakes and explain them briefly?

Brakes can be classified on the basis of their medium used to brake, they are as follows: > Hydraulic Brakes: These brakes as their name suggest use a fluid medium to push or repel the brake pads for braking. > Electric Brakes: These brakes use electrical energy to deplete or create a braking force.Both the above types of breaks are used primarily for applications where a large amount of energy is to be transformed. > Mechanical Brakes: They can be further classified on the basis of the direction of their acting force: Radial Brakes: As their names suggests the force that acts on the brakes is of radial direction. They can further be classified into internal and external blades. Axial Brakes: In these types of brakes the braking force is acting in an axial direction as compared to radial brakes.

How Does Hydraulic Clutches Work?

By using a non-compressible fluid, it acts like a solid push rod.

The ______________ is used to scribe arcs, circles and step-off distances on a work piece.

Divider

Steel is an alloy between iron and...?

Carbon

What is the percentage of carbon present in pig iron?

Carbon content is generally 3.5-4.5%.

What minerals are used in the manufacture of cars?

Cars are made from many various minerals. The steel body is made from the iron-rich minerals like magnetite and hematite. Door handles and badges are often coated in chromium which comes from chromite. Some of the other minerals used are aluminum, quartz, copper, magnesium, zinc, tin etc.

What state the first law of Thermodynamics?

Conservation of Energy

Between steel, copper and brass, which conduct faster heat.

Copper conducts heat faster than steel or brass. In most cases, material that is good for conducting heat is also good for electricity.Copper conducts heat faster than steel or brass. In most cases, material that is good for conducting heat is also good for electricity.

_____________________ is the property of a metal to be drawn into fine wires.

Ductility

Which is the hardest material on earth?

Diamond is currently the hardest material, made up of carbon atoms which cannot move. Carbon is the only atom that can have four electrons in the second shell surrounding the carbon nucleus, precisely why making a diamond the hardest material. However, there also are claims by a few to a new rare material called Wurtzite Boron Nitride which has a structure similar to a diamond but has some other atoms in place of carbon.

Which chisel is used to clean out corners and pull over off-drilled centers?

Diamond point

What is DTSI? Why it is used in motor bikes?

Digital Twin Spark Ignition. This is used for a better fuel combustion in the cylinder head which helps provide better efficiency and optimum use of fuel.

Explain why diesel engine is known as high torque and petrol engine as high speed engine?

Each power stroke in a petrol engine releases more heat and is converted into mechanical energy due to a higher rate of burning. This is the reason petrol engine has higher power and acceleration. Diesel engine is a compression ignition engine with higher compression ratio, therefore extreme pressure is high. Since the piston of a diesel engine is larger, more torque is delivered in produced.

The potential energy of a vertically raised body is __________ the kinetic energy of a vertically falling body.

Equal to

Files are layout tools made from high carbon steel

False

Flexible blades are hardened throughout and are often found in the workshop.

False

Phillips screw drivers are also known as standard screw drivers.

False

The dot punch usually has a point angle of 90°.

False

The outside caliper is used for checking inside diameters.

False

The pitch of a thread is measured perpendicular to the axes of the thread.

False

The tool rest is fixed over the wheels to protect the user from the grinding wheels

False

The part of the file used to prevent the handle from splitting is called the _________________.

Ferrule

The ____________________ chisel is used for general chiseling.

Flat

What describes the Navier Stokes equations?

Fluid Mechanics

What is a time and motion theory?

Frederick Taylor was pioneer of the time and motion theory. This technique monitors the amount of time required to complete a task along with observing the steps taken by a worker to complete the given task.

How can the reaction of support of a frame be evaluated?

Generally roller or hinged support are used to support the frames. The conditions of equilibrium are used to determine the reaction support of a frame. The condition of equilibrium takes place when the sum of the horizontal and vertical forces sum equal to zero. The system must form a state of equilibrium even after considering the external loads and the reactions at the supports. For equilibrium to be prevalent in the system the following conditions are required to be in occurrence: > Summation of V = 0. This implies that the summation of all the forces in the vertical direction results to zero. > Summation of H = 0 . This implies that the total of all the forces acting in horizontal direction is also zero. > Summation of M = 0. The sum of all the moment of forces around a point must be zero.

The flexible blade is usually ______________________.

Hardened at the teeth

What is heat treatment and why is it done?

Heat treatment can be defined as a combination of processes or operations in which the heating and cooling of a metal or alloy is done in order to obtain desirable characteristics without changing the compositions. Some of the motives or purpose of heat treatment are as follows: > In order to improve the hardness of metals.> For the softening of the metal. > In order to improve the machinability of the metal.> To change the grain size. > To provide better resistance to heat, corrosion, wear etc. Heat treatment is generally performed in the following ways: > Normalizing > Annealing > Spheroidising > Hardening > Tempering > Surface or case hardening

Most drills in the work shop are made from ____________.

High speed steel

In a simple spring-mass system, stability with oscillations is obtained when the differential equation laplace transform have..?

Imaginary negative roots

During the design of a friction clutch what are the considerations that should be made?

In order to design a friction clutch the following points must be kept in mind: > The material for the contact surfaces must be carefully selected. > For high speed devices to minimize the inertia load of the clutch, low weight moving parts must be selected. > The contact of the friction surfaces must be maintained at all the times without the application of any external forces. > Provisions for the facilitation of repairs must be there. > In order to increase safety the projecting parts of a clutch must be covered. > A provision to take up the wearing of the contact surfaces must be present. > Heat dissipaters to take away the heat from the point of contacting surfaces must be there.

Explain the formula of heat loss in a pipe.

In order to find total heat loss through the pipes it is imperative to know the thermal conductivity and the differing thicknesses of each layer. The ground that surrounds the pipe also acts as a layer of insulation. Considering this, the thermal properties of the stoneless sand is included in the heat loss calculation.

What Is The Mechanical Advantage Of A Double Pulley?

It only takes half the effort to move an object but twice the distance.

The size of a screw driver is determined by the ____________________.

Length of the shaft

What Is Knurling?

Machining process normally carried our on a centre lathe. The act of Knurling creates a raised criss-cross pattern on a smooth round bar that could be used as a handle or something that requires extra grip.

How many types of suspensions are used in automobiles?

McPherson struts Leaf spring Coil spring Torsion beam Wishbone Air Suspension

The rate of change of momentum is directly proportional to the impressed force, and takes place in the same direction in which the force acts. This statement is known as

Newton's second law of motion

Who invented the four stroke engine? According to you which one is more efficient, four stroke engine or a two stroke engine and why?

Nikolaus Otto invented the four stroke engine. Both, two stroke and four stroke have their own advantages and disadvantages. 4 stroke is more fuel efficient. However, 2 stroke produces more power.

Which layout tool is used to mark lines parallel to a finished edge?

Odd-leg caliper

Types of grinding machines?

Pedestal grinder' Bench grinder Buff and grinder

What is PS?

Personal Statement. It is something that gives an informative background about an individual.

What kind of pipes are used for steam lines?

Pressure and temperature are two of the most important factors to be considered before selecting the type of material to be used. Steam is a compressible gas due to which the capacity of the pipe line depends on the size of the pipes and pressure of the steam. Since steam at even low pressure can be dangerous, extra care is to be taken. Galvanized pipes are usually not used for steam. Pipes made of mild steel with welded fittings are instead largely used.

What does a pump develop?

Pump is a device that is used to transfer fluid from one place to another place which means it develops flow not pressure.

The ______________ is the bottom surface joining the sides of two adjacent threads.

Root

The ______________ is used to mark lines on the work piece during the layout process.

Scriber

Which grade of file has the closest spacing between their teeth?

Second cut

On what basis can sliding contact bearings be classified? Explain?

Sliding contact bearings can be classified on the basis of the thickness of the lubricating agent layer between the bearing and the journal. They can be classified as follows: > Thick film bearings: These type of bearings have their working surface separated by a layer of the lubricant. They are also known as hydrodynamic lubricated bearings. > Thin film bearings: In this type of bearings the surfaces are partially in direct contact with each other even after the presence of a lubricant. The other name for such type of bearings is boundary lubricated bearings. > Zero Film Bearings: These type of bearings as their name suggests have no lubricant present between the contact layers. > Externally or hydrostatically pressurized lubricated bearings: These bearings are able to without any relative motion support steady loads.

Dies used in thread cutting?

Solid Circular split Adjustable screw plate

Describe briefly the different cold drawing processes.

Some of the important cold drawing processes are as follows: > Bar and Rod Drawing: In the case of bar drawing the hot drawn bars are at first pickled, washed and coated to prevent oxidation. Once this is done a draw bench is used for the process of cold drawing. In order to make an end possible to enter a drawing die the diameter of the rod is reduced by the swaging operation. This end is fastened by chains to the draw bench and the end is gripped by the jaws of the carriage. In this method a high surface finish and accuracy dimensionally is obtained. The products of this process can be used directly without any further machining. > Wire Drawing: Similar to the above process the bars are first pickled, washed and coated to prevent any oxidation. After this the rods are passed through several dies of decreasing diameter to provide a desired reduction in the size ( diameter ). The dies used for the reduction process is generally made up of carbide materials. >Tube Drawing: This type of drawing is very similar to the bar drawing process and in majority of cases it is accomplished by the use of a draw bench.

What are the basis on which the best material for Sliding Contact Bearings manufacturing?

Some of the important properties to lookout for in the material for sliding contact bearings are as follows: > Compressive Strength: In order to prevent the permanent deformation and intrusion of the bearing the material selected should be possess a high compressive strength to bear the max bearing pressure. > Fatigue Strength: the material selected for the bearing should be able to withstand loads without any surface fatigue cracks getting created. This is only possible if the material has a high level of fatigue strength. > Comfortability: The material should be able to adjust or accommodate bearing inaccuracies and deflections without much wear and heating. > Embeddability: The material should allow the embedding of small particles without effecting the material of the journal. > Bondability: The bearings may be created by bringing together ( bonding ) multiple layers of the material. Due to the above reason the bondability of the material should be sufficiently high. > Thermal conductivity and corrosion resistance: Thermal conductivity is an essential property for bearing materials as it can help in quickly dissipating the generated heat. Also the material should have a level of

What are the rules that must be kept in mind while designing castings?

Some of the points that must be kept in mind during the process of cast designing are as follows: > To avoid the concentration of stresses sharp corners and frequent use of fillets should be avoided. > Section thicknesses should be uniform as much as possible. For variations it must be done gradually. > Abrupt changes in the thickness should be avoided at all costs > Simplicity is the key, the casting should be designed as simple as possible. > It is difficult to create true large spaces and henceforth large flat surfaces must be avoided. > Webs and ribs used for stiffening in castings should as minimal as possible. > Curved shapes can be used in order to improve the stress handling of the cast.

What are the points that should be kept in mind during forging design?

Some of the points that should be followed while forging design are: > A radial flow of grains or fibers must be achieved in the forged components. > The forged items such as drop and press forgings should have a parting line that should divide the forging into two equal halves. > The ribs in a forging should not be high or thin. > In order to avoid increased die wear the pockets and recesses in forgings should be minimum. > In forgings the parting line of it should lie as far as possible in a single plane. > For ease of forging and easy removal of forgings the surfaces of the metal should contain sufficient drafts.

What kind of materials should be used for shafts manufacturing?

Some of the qualities that should be present in materials for shafts are as follows: > The material should have a high index of strength. > Also it should have a high level of machinability. > The material should possess a low notch sensitivity factor. > The material must also have wear resistant properties. > Good heat treatment properties should also be present The common material used to creates shafts of high strengths an alloy of steel like nickel is used. The shafts are manufactured by hot rolling processes and then the shaft is finished using drawing or grinding processes.

Which of the following is not a scalor quantity. BA.Force B.Speed C.Velocity D.Accelaration

Speed

The _______________ carries the grinding wheels and is driven by a belt connected to the motor.

Spindle

What are the different types of springs and explain them briefly?

Springs can be broadly classified into the following types: > Helical Springs: These springs as their name suggests are in coil form and are in the shape of helix. The primary purpose of such springs are to handle compressive and tensile loads. They can be further classified into two types: compression helical spring and tension helical spring each having their own unique areas of application./ > Conical and volute springs: Both these spring types have specialized areas of usage where springs with adaptable rate according to the load is required. In case of conical springs they are wound so as to have a uniform pitch while on the other hand volute springs are wound in a slight manner of a parabloid. > Torsion Springs: The characteristics of such springs is that they tend to wind up by the load. They can be either helical or spiral in shape. These types of springs are used in circuit breaker mechanisms. > Leaf springs: These types of springs are comprised of metal plates of different lengths held together with the help of bolts and clamps. Commonly seen being used as suspensions for vehicles. > Disc Springs: As the name suggests such types of springs are comprised of conical discs held together by a bolt or tube. > Special Purpose Springs: These springs are all together made of different materials such as air and water.

The proper sequence of tapping a blind hole is ___________________________.

Tapered, plug, bottoming

The process of cutting internal threads by hand is known as:

Tapping

What do you understand by the Hooke`s Coupling what are its purposes?

The Hooke`s coupling is used to connect two shafts whose axes intersect at a small angle. The two shafts are inclined at an angle and is constant. During motion it varies as the movement is transferred from one shaft to another. One of the major areas of application of this coupling is in gear boxes where the coupling is used to drive the rear wheels of trucks and other vehicles. In such usage scenarios two couplings are used each at the two ends of the coupling shaft. they are also used to transfer power for multiple drilling machines. The Hooke`s coupling is also known as the Universal coupling. The torque transmitted by the shafts is given by :T= (pie/16) x t x (d) cubeWhere T = torque, t = shear stress for the shaft material and d the diameter of the shaft.

What are the assumptions made in simple theory of bending?

The assumptions made in the theory of simple bending are: > The material of the beam is homogeneous this implies that it is uniform in density, strength and have isotropic properties meaning possessing same elastic property in all directions. > Even after bending the cross section of the beam remains constant. > During the initial stages the beam is straight and unstressed. > All the stresses in the beam are within the elastic limit of its material. > The layers of the beam are free to contract and expand longitudinally and laterally > On any cross section the perpendicular resultant force of the beam is zero. > Compared to the cross-sectional dimension of the beam the radius of curvature is very large.

Why do heavy vehicles use diesel engine?

The compression ratio of diesel engine is higher than the petrol engine, the reason for producing higher torque. The efficiency of diesel engine increases with load. Diesel produces slow energy on burning of fuel and the efficiency of the engine increases with load which is why diesel engine is suitable and largely used for heavy vehicles.

What are the advantages of DTSI over normal engines?

The cylinder head has two spark plugs, instead of the usual one. When two sparks are generated at either ends of the combustion chamber, the air-fuel mixture is ignited in a way that creates two flame fronts. A higher rate of combustion is achieved leading to higher rise in pressure. The outcome of this is more torque, better fuel efficiency and lower emissions.

What are the factors that can affect the Factor of safety selection?

The factor of safety is used in designing a machine component. Prior to selecting the correct factor of safety certain points must be taken into consideration such as: > The properties of the material used for the machine and the changes in its intrinsic properties over the time period of service. > The accuracy and authenticity of test results to the actual machine parts. > The applied load reliability.> The limit of stresses (localized). > The loss of property and life in case of failures.> The limit of initial stresses at the time period of manufacture. > The extent to which the assumptions can be simplified. The factor of safety also depends on numerous other considerations such as the material, the method of manufacturing , the various types of stress, the part shapes etc.

Why is stress considered important in a shaft?

The following types of stresses are prevalent in shafts:> At the outermost surface of the shaft the max shear stress occurs on the cross-section of the shaft. > At the surface of the shaft on the longitudinal planes through the axis of the shaft the maximum longitudinal shear stress occurs. > At 45 degrees to the maximum shearing stress planes at the surface of the shafts the major principal stress occurs. It equals the max shear stress on the cross section of the shaft. > For certain materials where the tensile and compressive strengths are lower in measure as compared to the shear strength, then the shaft designing should be carried out for the lowest strengths. > All these stresses are of significance as they play a role in governing the failure of the shaft. All theses stresses get generated simultaneously and hence should be considered for designing purposes

What are the different values that need to be determined in order to design a cylinder for an ICE?

The following values are needed to be determined: > Thickness of the cylinder wall: The cylinder walls in an engine is made witness to gas pressure and the side thrust of a piston. This results in two types of stresses: longitudinal and circumferential stress. Both the types of stresses are perpendicular to each other and hence it is aimed to reduce the resulting stress as much as possible. > Length and bore of the cylinder: The length of the cylinder and the length of the stroke is calculated on the basis of the formula: length of cylinder L = 1.15 times the length of the stroke (l). L = 1.15(l) > Cylinder flange and studs: The cylinders are always cast integral as a part of the upper crankcase or in some cases attached to it by means of nuts and bolts. The flange is integral to a cylinder and henceforth its thickness should be greater than that of the cylinder wall. The thickness of flange should generally be between 1.2t-1.4t where t is the cylinder thickness.The stud diameter is calculated by equating gas load ( due to max pressure ) to the grand total of all the resisting forces of the studs.

Why gas containers are mostly in a cylindrical shape?

The ideal shape would be a sphere. The container must have the capacity to withstand the extremely high pressure of liquefied gas. A spherical shape helps in distributing these forces uniformly.

What are the different theories of failure under static load, explain briefly?

The main theories of failure of a member subjected to bi-axial stress are as follows:> Maximum principal stress theory ( Rankine's theory): This theory states that failure occurs at a point in member where the maximum principal or normal stress in a bi-axial system reaches the maximum strength in a simple tension test. > Maximum shear stress theory ( Guest's or Tresca's theory): This theory states that failure occurs when the biaxial stress reaches a value equal to the shear stress at yield point in a simple tension test. > Maximum principal strain theory ( Saint Venant theory): This theory states that failure occurs when bi-axial stress reaches the limiting value of strain. > Maximum strain energy theory ( Haigh's theory): This theory states that failure occurs when strain energy per unit volume of the stress system reaches the limiting strain energy point. > Maximum distortion energy theory ( Hencky and Von Mises theory): This theory states that failure occurs when strain energy per unit volume reaches the limiting distortion energy.

Explain the difference between projectile motion and rocket motion.

The major difference is that a projectile has no motor or a rocket on it, due to which the momentum is given to it as it is launched. A pen thrown across a room is a classic example of a projectile motion. On the other hand, a rocket or missile has a motor on it which helps in accelerating while moving. This helps in resisting other forces such as gravity. A projectile does not have any specific shape, it is a point mass, whereas rocket has a particular shape having its center of gravity situated at a particular point on its body. Thus rocket motion comes under kinetics and projectile comes under kinematics.

What are considerations taken into account while creating a piston head?

The piston head is designed on the basis of the following considerations: > The crown should have enough strength to absorb the explosion pressure inside the engine cylinder. > The head must always dissipate the heat of the explosion as quickly as possible to the engine walls. The thickness of the head is calculated on the basis of another formula which takes into consideration the heat flowing through the head, the conductivity factor of the material. The temperature at the center and edges of the head. > The thickness of the piston head is calculated on the basis of the Grashoff`s formula which takes into consideration the maximum gas pressure of an explosion , the permissible bending and the outside diameter of the piston.

What is the ratio of specific heat of air?

The ratio of specific heat γ=CP/CV is a factor in adiabatic engine processes and in determining the speed of sound in gas. This ratio γ=1.66 for an ideal monoatomic gas and γ=1.4 for air, which is predominantly a diatomic gas.

What do you understand by the concept of a 6 stroke engine? Explain how it works.

The six stroke engine is based on the concept of four stroke engine but built with an intention of improvising the efficiency in reducing emission. Every cycle of a four stroke engine involves the upward and downward movement of the piston which happens twice in the chamber, resulting in four total strokes and one of which is the power stroke which provides the torque to move the vehicle. A six stroke engine works similarly except that there are two power strokes.

In order to derive the torsional formulas what are the assumptions taken?

The torsion equation is derived on the basis of following assumptions: > The shaft material is uniform, throughout the shaft. > Even after loading the shaft circular remains circular. > After the application of torques the plain section of a shaft remains plain. > Any twist that occurs in the shaft remains uniform and constant. > After the application of torque the distance between any two cross-sectional references remains constant. > The elastic limit value of a shaft is never exceeded even after the shear stress induced because of torque application.

Explain in an orderly manner how the force in the member of a truss be detected using the method of joint.

The steps required to calculate the force are as follows: > The reaction at the support has to be first calculated. > Once the reaction is calculated the direction of force of the member is made to make it tensile. On getting the result to be negative the direction assumed is wrong and this implies the force being compressive in nature. > A joint needs to be selected whose 2 members are not known. The lami`s theorem is used on the joint on which less than three forces are acting. > After the above process is complete the free body diagrams of the joint needs to be made. Since the system is in equilibrium the condition of Summation of V and H must result in zero. > After the above step the resolution of forces method needs to be used on the joint on which more than 4 forces are acting.

State the laws of thermodynamics and its importance of in Mechanical Engineering.

Thermodynamics is a physical science which studies the interrelation between heat, work and the internal energy of any system. Thermodynamics helps study all the systems of mechanical engineering. There are three laws of thermodynamics. First Law: Energy can be neither created nor destroyed. It can only change forms. In any process in an isolated system, the total energy remains the same. Eg: turning on a light would seem to produce energy; however, it is electrical energy that is converted. Second Law: The second law of thermodynamics states that the entropy of any isolated system not in thermal equilibrium almost always increases. Eg: A car that has run out of gas will not run again until you walk 10 miles to a gas station and refuel the car. Third Law: As temperature approaches absolute zero, the entropy of a system approaches a minimum. Eg: Water in gas form has molecules that can move around very freely. Water vapor has very high entropy (randomness). As the gas cools, it becomes liquid which can still move around but not as freely. At this point they have lost some entropy. On cooling further it becomes solid ice where molecules can no longer move freely but can only vibrate within the ice crystals. The entropy is now very low. As the water nears absolute zero, the vibration of the molecules diminishes. If the solid water reaches absolute zero, all molecular motion would stop completely. And at this point the water would have no entropy at all.

Explain what is torque

Torque is the force that causes rotation. It is a measure of how much force is acting on an object making it rotate.

All-hard blades are hardened throughout their length

True

Cuts of files refer to the pattern their teeth.

True

Dies are not used to cut all types of threads on a work piece

True

Drilling is the process of creating a hole in a work piece using a drill.

True

Phillips screw drivers usually have a star-shaped tip.

True

Pillar drilling machine is a type of drilling machine often found in the workshop

True

Solid dies are used for chasing or re-cutting threads that are damage.

True

Tap drill size is the drill size that would leave adequate material in the hole for the tap to cut a thread.

True

Taps are used to cut internal threads on a work piece.

True

The combination set consists of a steel rule, square head, and a centre head.

True

The crest of a thread is the top surface joining the sides of a thread.

True

The grinding head is the top of the grinding machine housing the spindle.

True

The hacksaw should be used at 40 - 50 strokes per minute.

True

The pitch of a hacksaw blade is the number of teeth per inch.

True

The _______________ is used to layout lines at right angle to a machined edge.

Try-square

Work holding devices used on the drill press?

V-block and clamp Drill vise Angle plate

___________________ pliers provide extremely high gripping power because of the adjustable lever action.

Vise-grip

The minimum force required to slide a body of weight W on a rough horizontal plane is

W tan θ

A drill socket is used?

When the hole in the spindle of the drill press is too small for the shank of the drill.

What is the difference between torque and power?

While power determines the speed of a vehicle, torque determines the time in which that speed can be reached. The greater the torque figure, the faster the acceleration. The more torque in the engine, the faster you accelerate. Power is the rate at which work is done, so it is basically the potential of the engine.

Tension is given to the blade of the hacksaw using the ____________________.

Wing nut

The point, through which the whole weight of the body acts, irrespective of its position, is known as

centre of gravity

In ideal machines, mechanical advantage is __________ velocity ratio.

equal to