CS MAINS
MECHANICAL ENGINEERING
Paper-I
Time Allowed Three Hours

Maximum Marks: 250

QUESTION PAPER SPECIFIC INSTRUCTIONS
Please read each of the following instructions carefully before attempting questions
There are EIGHT questions divided in Two Sections and printed both in HINDI and in ENGLISH.
Candidate has to attempt FIVE questions in all.
Question Nos. 1 and 5 are compulsory and out of the remaining, THREE are to be attempted choosing
at least ONE from each section.
The number of marks carried by a question/part is indicated against it.
Answers must be wriften in the medium authorized in the Admission certificate which must be stated clearly
on the cover ofthis Question-cum-Answer booklet in the space provided. No marks will be given for
answers written in medium other than the authorized one.
Wherever any assumptions are made for answering a question, they must be clearly indicated.
Diagrams/Figures. wherever required. shall be drawn in the space provided for answering the question
itself.
Unless otherwise mentioned, symbols and notations carry their usual standard meaning.
Allempts ofquestions shall be counted in chronological order. Unless struck off, attempt ofa question shall
be counted even if attempted partly. Any page or portion of the page left blank in the answer book must
be clearly struck off.
I

SECTION-A

Q. A particle of mass m is resting at point on a smooth semicircular cylinder of radius tied to a point A vertically above the centre of the cylinder at a height of 2 with a string of length 1.1 r as shown in Fig. If the string is cut, find the angle thita defining the position C of the particle where it jumps off the cylinder.
src='./qimages/282-1a.jpg'><br><br> 10

Q. Stresses at a point are shown in Fig. What is the shear stress on plane AC, if t on plane BC is 40 MPa What is the magnitude of angle ethita if AB is a principal plane? What is the maximum shear stress at the point
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Describe different crystal systems in Materials.
Q. A pinion having 30 teeth drives a gear having 80 teeth. The profile of the gears is involute with 200 pressure angle, 12 mm module and 10 mm addendum. Find the length of path of contact, arc of contact and contact ratio.
Q. The vibrations of a machine of mass 76 kg are damped by a viscous dashpot which diminishes amplitude of vibrations from 17.2 mm to 3.2 mm in two complete oscillations. The machine is mounted on four springs each of stiffness 7.5 N/mm. Assuming that the damping force varies as the velocity, determine

the damping coefficient,
the ratio of frequencies of damped and undamped vibrations, and
the periodic time of damped vibrations.

Q. Derive expressions for longitudinal and hoop stresses in a thin walled pressure vessel. Using the above expressions, determine hoop and longitudinal stresses in a household LPG cylinder, assuming it to be a thin walled pressure vessel with following dimensions:

OD 315 mm thickness: 2.8 mm. Take end caps to be flat and the pressure in the cylinder is 1.4 MPa at room temperature. 20

b)Describe Austempering of steel with help of TTT diagram. 10
Q. A cam drives a flat reciprocating follower in the following manner During first 1200 rotation of the cam, the follower moves outwards through a distance of 20 mm with simple harmonic motion. The follower dwells during next 30° of cam rotation. During next 120° of cam rotation, the follower moves inwards with simple harmonic motion. The follower dwells for the next 900 of cam rotation. The minimum radius of the cam is 25 mm.
Draw the profile of the cam. 20

Q.
a shaft is to transmit 2 kw at 750 r.p.m. the shaft is supported in bearings a and 300 mm apart. two pulleys of 300 mm diameter and 150 mm diameter are located at b and d as shown in fig. assume that the belt tensions are vertical for both pulleys. ratio of belt tensions for both pulleys is 3. neglect weight of pulleys and shaft. take combined fatigue and shock factor in bending and twisting equal to kb 1.5, kt 1.0, respectively.
Determine uniform diameter of the shaft if allowable tensile stress is 110 MPa and allowable shear stress is 65 MPa. (Take shaft diameter in steps of 5 mm.) 20
src='./qimages/282-3a.jpg'><br><br>

Q. What are polymeric materials Distinguish between two polymer types. 10
Q. 20
Because of nature of its operations, the load torque of a machine is intermittent as follows: During its three quarter revolution, the load torque increases uniformly from 10 kNm to 15 kNm. Thereafter it remains constant for half revolution and then decreases uniformly in three quarter revolution to 50 kNm. After this for one revolution it remains constant. Thus the cycle is repeated. The machine is run by a constant torque motor running at a speed of 300 rpm, in conjunction with a flywheel of mass moment of inertia of 2200 kg/m2.
Determine
Magnitude of mean torque of motor
Power of the motor
Speed fluctuation of the system.

Q. A solid circular shaft is subjected to a bending moment of 3 kN-m and a torque of 1 kN-m. The shaft is to be made in carbon steel for which (sigma)y 480 MPa and ty 265 MPa.
Calculate shaft diameter using
Maximum normal principal stress theory
Maximum shear stress theory.
Q. What are composites? How are they classified Mention any four applications of composites.
10
Q. An epicyclic speed reduction gear schematic is shown in Fig. Compound wheel
B-C is free to rotate on pin A connected to driving shaft. Wheel meshes with fixed
wheel and wheel meshes with wheel keyed to driven shaft.
If number of teeth on wheels are Tb 27, Tc 30, Td 24 and Te 21, determine the
ratio of speeds of the driving and driven shafts. 20
src='./qimages/282-4c.jpg'><br><br>

SECTION-B
Q. Compare flank wear and crater wear and draw tool life versus cutting speed curves for H.S.S., Carbide, and ceramic tools. 10
Q. Define 'Grinding Ratio'. Also explain what is meant by a grinding wheel acting soft or acting hard. Is it always desirable to obtain a high grinding ratio in practice 10
Q. A company studied the cost data on quality and found a relationship between the percent defective and the cost of control and cost of failure per 100 parts as under
Cost of failure F 1500 120 X
Cost ofControl C 3000/X
where X is percent defective.
What is the percent defective which minimizes the quality cost How much is the minimum quality cost per hundred parts 10
Q. Fixed and variable costs for three potential manufacturing facilities for same product are
shown below

Mfg. Facility Fixed CostlYr.(Rs.) Variable Cost/Unit(Rs.)
A 1,25,000 50
B 2,00,000 40
C 2,50,000 20
If the expected output is to be 8000 units per year, which facility should be selected? Explain with the help of a graph.
When is option B economical?
Comment on choice of the options. 10

Q. Differentiate between open loop, closed loop and adaptive control systems used in NC machine tools. 10
Q. According to the ISO system, sketch the basic size, deviation, and tolerance on a shaft and hole assembly. Why uni-lateral tolerance is preferred over bi-lateral tolerance 10
Q. Explain with the help of a sketch the Electric Discharge Machining process. What are its advantages and limitations? Describe the nature of the surface obtained by EDM. Also name any three important electrode materials. 20
Q. Explain with neat sketches the Plasma Arc Welding process and discuss its applications and limitations. 20

Q. List five distinct methods used to obtain high energy rates in HERF. With the help of a sketch explain the spark discharge method of High Energy Rate Forming. Also mention two advantages and three important applications of HERF method. 20
Q.
State the basic principles of plant layout. Table below 12 work-elements along with their immediate predecessor elements and duration in minutes. Design suitable line consisting of appropriate work-stations assumirig a cycle time of 70 minutes. Compute the line efficiency, balance delay and smoothness index
src='./qimages/282-7b.jpg'><br><br>
Use the least-number- of predecessors rule. 20

Q.
A transport company assumes that the requirement of tyres used in vehicles are closely related to number of kilometres driven. Accordingly, the following data covering the last six months have been collected as follows
Months Tyres Used Thousands of km driven
1 100 1500
2 150 2000
3 120 1700
4 80 1100
5 90 1200
6 180 2700
Establish the relationship (linear) between the required tyres and kms driven based on data. How good is the co-relation
If expected kms drive in a month is 32,00,000, forecast the demand for tyres. 10
Q.8(a)
Compare the concept of 'Just-in-Time' with that of 'Manufacturing Resource Planning'. A work center uses Kanban containers which hold 200 parts. To produce enough parts to fill the container 60 minutes are needed. Moving the container to the next work-station and return of empty container takes 120 minutes. There is overall demand rate of 6 units per minute.

Calculate the number of containers needed for the system.
What is maximum inventory in the system
If the setup and run time to fill the container is reduced to 40 minutes, can the number of containers be reduced? How much will be the inventory in system then?
.20
Q.
What is understood by "process is under statistical control" Explain clearly with the help of diagrams, illustrating out of control situations. Plot the control charts of X and using the following sample data and a sample size of 5. From the chart, find out whether the process is under control.
src='./qimages/282-8b.jpg'><br><br>

Q.
A manufacturing organization is considering investment in two alternative equipment's A and B. Equipment A costs Rs. 30,000 while the equipment B costs Rs. 50,000. The expected yearly net income for the first five years from these equipment's are Rs. 10,000 and Rs. 15,000 for equipment's A and B respectively. Assuming the cost of capital as 12% per annum, determine which equipment should be selected. Use net present value approach. 10