CS (MAiN) EXAM, 2010

MECHANICAL ENGINEERING

Paper I
Time A/iowed Three Hours IIMaximum Marks . 300I
INSTRUCTIONS
Each question is printed both in FIindi and in English.
Answers must be written in the lnedium specified in the Certificate issued to YOU;. which must be stated clearly on the cover ofthe answer-book in the space provided for the purpose. No rnarlls will be given for the answers written in a medium other than that specified in the Admission Certificate.
Candidates should attentpi Questions 1 and 5 which drecornpulsory" and any three ofthe renz.aining questions selecting at least one question Tram each Section.
The 'nulnber of marks carried by each question lS indicated at the end or the question.
Symbols I notations carry their usual
m.eanings, unless otherwise indicated. If any data is considered assume suitable value and indicate the same clearly.
Newton lnay be converted to kg using the equality 1 kilonewton JzN) 100 if found necessary.
00/.., if 31jJ!iif CfST f49C1 [9ClJ J
SECTION A

1. The state of stress at a givon point in a loaded component is given by cry and 'txy and the principal stresses at the point arc cr1 and If the ne"v axes at the point are changed to and such that state of stress w.r.t. the new axes are sigma sigma
and
Show that: sigma x+sigma y=sigma x'+sigma y'-sigma1+sigma2' 6
Sketch the Mohr's stress circle for pure shear stress state and hydrostatic state of stress. 3
A cast iron bar of 30 mIn dia:metcr and 1 ITl length is subjected to equal and opposite torque T aJ?plied at its ends. If tensile strength of cast iron is 80 MT)at what is the maxi.muTll value of torque Show the plane of failure for the applied sense of torque T. 3
A hollow shaft whose internal diaITIeter IS half of the external diaITlcter is subjected to InaxiITlurn bending rrlOInent of 2 kN-m at a section and constant torque of 4 kN-In all along its length. If .yield stress of the shaft Tnatcrial is 280 MPa and factor of safety is vvhat should be the minimum safe diameters of the shaft? 9
What is the difference betwccn centrifugal and inertia type of governors? Which one is Tnorc sensitive? Why is the former preferred to the 1a tter 3
Distinguish bet'Ncen the pressure angle of a radial caITl and that of a spur gear, "vith the help of a sketch. 8
What type of Illation IS perforlllcd by a point on the surface of a football rolling on the ground and a point on the surface of a nut llloving over a threaded bGlt 4
Distinguish between Eutectoid and Eutectic. in the case of Fe ­C systeTTI. Give the cOITlposition and the lllaximuIll temperature at which eutectoid and eutectic arc formed. 12
A solid cylinder ofIIIass Ill. and radius r starts Tolling down an inclined plane. what win be the velocity of its centre of mass after it has come down by 8m In vertically (Assume g 9 ·81 rn/s2 4



The crane shov.rn in Figure above is supported by cables BD and BE. The distances ITlarked arc in lTl. What arc the tensions in the cables BC, 13D and BE, vvhen Be is parallel to the x-axis? 8
2. A hollow shaft is subjected to a steady bending rnorrtent of40 and twisting moment of50 N-rn. Outer diaDleter of the shaft is t'Wice the inside diameter. Calculate the diameters of the shaft using ASME Code for transIllission shafting on the basis ofIllaximuJn shearing stress theory offailure. 30
Take: Yield point stress in tension of shaft :material 280 MPa Factor of safety 2-0 Combined bending and fatigue shock factor 1-5 COlTIbined shock and fatib'Ue -ractor for twisting 1·0

What is a quick-return ITlcchanisITl Give its types and applications. Ho"W is the ratio of time of cutting stroke to return stroke calculated for a slotted lever and crank type 01 quick-return TI1echanisITl Explain with the help of a neat sketch. 15
Which type of epicyclic gear train is used for rear v.rheel drive of autoInotivc trucks? Sho'v that rpITI of the propeller shaft IS arithmetical TIlcan ofrpD1 oftwo rear vvhcels, while negotiating a road curvc. 15
3.

Figure shows a polyspast lifting a weight Q
equalling 1000 N by another 'Weight of P
equalling 300 N. Neglecting friction and the
ITlasses of the pulleys and cables and the
inclinations ofcables. deterlTline the distance
moved by Q in 2 seconds fTOTTI start. J 8



8mall ·steel balls fall froIll rest through the opening at A at a steady rate of t"VQ per second. Find the vertical separation h of two consecutive balls when the lower one has dropped 5 III from A.
C

A body A weighing Pl descends dovvn an inclined plane D which makes an angle ex ""vith the horizontal and pulls a load B that 'veighs P 2 by ITleans of a weightless and inextensible string passing over a pulley C as sho'wn in Figure. Determine the horizontal component of the pressure 'Nith which the inclined plane D acts on the floor rib E. 20

A satellite is orbiting around the Earth at an
altitude of 320 kIn. Assullling the Earth
radius as 6500 kITl and both the orbit and the
Earth as circular. deter.mine the speed of the
satellite. 10
4. What is T'in Babbitt? What is the composition and
lTlajor application of th·is aHoy? How is it different
f"roITl other Babbitts? 20
What is the application of glass fibre reinforced
plastic (epoxy) How do these composites COITlpare
with carbon reinforced plastics (epoxy) 20
Explain the transforIllation of iron frolll Bee to
FCC. What properties change when iron changes
lroIll Bee structure to FCC structure? 20


SECTION B


5. COlTIpare Work SaJnpling"With 'Time Study'. When
are they used for calculating standard time of
performing short cycle jobs? Give respective areas
of application. 12
XYZ Corporation has a production (and sales)
capacity of 10,00,000 per ITlonth. Its fixed costs
arc 3,50,000 per :month and the variable costs
over a considerable range of volume are 0·50 per
Rupee of sales.
Determine annual break-even point and
develop break-even graph.
Determine the effect on break-even point if
fixed costs were decreased by 100/0 and the
variable costs per unit are increased by the
same percentage. 8+4=12
In a metal cutting operation, the follov.ring
equation for tool-life 'Was obtained for H.B.S. tool:


G-iven that: tool-life =60 ITIin,
cutting speed 40 :rnJrnin,
feed nun/rev,
depth of cut 2·0 ITun.
Cnmputc tool-life if speed, feed and depth of cut
are together increased by 25% and also if they are
increased individually by 250/0.




What is the difference bet"veen hole basis system and shaft basis systeIT1 Why is hole basis systeITl the more extensive in use?

What are the differences betW"een interchangeability and selective assembly? 12
Vhy 18 Total Quality Management important? What are the benefits that can be obtained by applying TQM In the software industries? 'What are the principles of TQM in such applications? 12
6. What are the various five fuel gases used for gas -velding? Givetheirche1T1.icalcomposition, forIYlula and specific heat content. Indicate -also the rrIaximuITl temperature reac:;hcd in the respective flames. What percentage of oxygen is supplied by the torch in. anyone of the fuel gases Give the chcIl1ical reaction.s in the various zones of the neutral flame. 30
Ho'i,V are Tlletal tooth-paste tubes made cOITunercially Dra'N the tools configuratiq.n ,"vith the help of a neat sketch. 3

7. Illustrate with the help of neat sketches the
differences between open-loop and
closed-loop control in NC Systelll_ Why is
feedback not possible in open-loop control
system? 22
In open-loop NC system the shaft of a
stepping I1lotor is connected directly to the
lead screVi x-axis of the tnachinc tabJe. The
pitch of the lead screw is 3-0 tnDl. The
nUIllber of step angles on the stepping n'lotor
is 200.
Detennine how closely the position of the
table can be controlled, assuming that there
are no mechanical errors in the positioning
systeIll. •
Also, what IS the required frequency of the
pulse train and the corresponding rotational
speed of the stepping Inotor in order to drive
the table at a travel rate of 100 IllrnJmin 8


Determine the trial central line and control liITlits for p chart using the following data, which are fOT the paYITlcnt of dental insurance claims. Plot the values on graph paper and determine if the process is stable. Ifthere are any out-of-control points) assum.e an assignable cause and determine the revised central line and control lim.its.
Subgroup Number Number Inspected NUInber Noncon­forming Subgroup Number Number Inspected Number Noncon­forming
1 300 3 14 300 6
2 300 6 15 300 7
3 300 4 16 300 4
4 300 6 17 300 5
5 300 20 18 300 7
6 300 2 19 300 5
7 300 6 20 300 o
8 300 7 21 300 2
9 300 3 22 300 3
10 300 o 23 300 6
300 6 24 300 1
12 300 9 25 300 8
13 300 5


Determine the triallirnits and revised control lim.its for a u chart using the data in the table for the surface finish of rolls of white paper. A.ssume any out-or-control points have assigt1.able causes.
Total Total
Lot Sample Lot Sample
Noncon-Noncon-NunlbcT Size
Number Size
fOrInities
forITli ties
10 45 1510 48
21051 161135
3 10 36 1710 39
4 9 48 1810 29
5 10 4-2 19 10 .37
6 10 5 201033
7 10 33 2110 15
8 8 27 2210 33
9 8 31 23 11 27

10 822 24 10 23
11 12 25 2510 25
1212 35 26 10 41
131232 27 9 37
1410 43

28 10 28
In both cases assunlc 3a lirn.it.



8. Toyota Production Systetn and lean
operations sustain co:rnpetitive advantage.
Distinguish 31110ng the three. SecondlYt discuss
how effective JIT contributes to cOITlpctitive
advantage. identify three core cOInponents
ofTPS.
A cost ITlatrix is provided, here alTIount available
exceeds the aITlount required.

8 1 D1 D2 D3 D4 Available
8 9 3 7 130
8 2 3 6 8 4 180
8 3 7 5 4 5 240
8 4 8 7 2 6 160
5 4 2 9 90
8 6 8 4 4 3 120
Required 300 100 150 200



Using Vogel's Approxim.ation determine initial feasible solution. Give all assulllptions and provide clear steps.
What is total transportation cost? How can this be checked for optilllality? Sho'wV one step only. 20+10=30
C-DTN-K-NFA 24



Note: English version of the Instructions is printed on the front cover of this question paper.