Showing posts with label IIT Kharagpur. Show all posts
Showing posts with label IIT Kharagpur. Show all posts

Friday, 12 June 2015

Automobile Engineering - Solved Problem - Engine Combustion Parameters & Efficiency



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Question:
An eight cylinder automobile engine of 85.7 mm bore and 82.5 mm stroke with
a compression ratio of 7 is tested at 4000 rpm. on a dynamometer which has a
0.5335 m arm. During a 10 minutes test at a dynamometer scale beam reading
of 400 N, 4.55 kg of gasoline for which the heating value is 46,000 kJ/kg are
burnt, and air at 294 K and 10 × 104 N/m2 is supplied to the carburetor at the
rate of 5.44 kg per minute. Find
a) the brake power (b.p) delivered
b) the brake mean effective pressure (bmep)
c) the brake specific fuel consumption (bsfc)
d) the specific air consumption
e) the brake thermal efficiency
f) the volumetric efficiency
g) the air-fuel ratio (A-F Ratio)

Solution: 2 6 ( ) . 2 2 4000 400 0.5335 89.34 kW 60000 60000 . 89.39 kW ( ) 8( ) ( ) . 2 60000 60000 . 60000 89.39 60000 704.39 kPa 4 4 .0825 (85.7) 4000 4 10 704. a b p T NT b p n bmep Al N bmep Al N b b p x bmep b p lAN bmep                            39 kPa ( ) Fuel consumed in one minute, 0.455 kg/min Fuel consumed in one hour, 0.455 60 kg/hr 27.3 kg/hr 27.3 kg/hr 0.306 kg/b.kWh . 89.34 kW 0.306 kg/b f f f f c w w w w bsfc b p bsfc              .kWh ( ) Air consumption rate, 5.44 kg/min 5.44 60 kg/hr 326.4 kg/hr 326.4 kg/hr 326.4 kg/hr 3.653 kg/b.kWh . 89.34 kW 3.653 kg/b.kWh a a a a d w w w bsac w b p bsac                2 4 3 ( ) Brake Thermal efficiency, . 89.34 kW 89.34 kJ/s 0.455 kg/min 46000 kJ/kg 0.455 46000 kg/s kJ/kg 60 0.256 25.6% ( ) Piston displacement (0.0857) (0.0825) 4.76 10 m 4 b f b b e b p w HV f                     4 3 3 /cycle At 4000 rpm and for four-stroke, eight-cylinder engine, Piston displacement 4.76 10 4000 8 m /min 7.62 m /min 2 Standard conditions of intake: Temperature (T) 298 K,        5 3 5 Pressure ( ) 1 atm 1.01325 10 Pa Volume of air used at intake conditions 5.44 287.1 298 4.593 m /min 1.01325 10 Volumetric efficiency, 4.593 100% 60.3% 7.62 60.3% ( ) A a v v p w RT p g                  ir : Fuel Ratio 5.45 11.98 0.455 A/F Ratio 11.98 a f w w       
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Energy Losses (Heat Balance)

Only a part of the energy supplied to the engine is transformed into useful work whereas
the rest is either wasted or utilized for heating purposes. The main part of the unutilized heat
goes to exhaust gases and to the cooling system. In order to draw a heat balance chart for an
engine, tests should be conducted to give the following information.
(i) Energy supplied to an engine which is known from the heating value of the fuel
consumed.
(ii) Heat converted to useful work.
{Hi) Heat carried away by cooling water.
(iv) Heat carried away by exhaust gases.
(v) Heat unaccounted for (radiation etc.)
It is expected that the heat balance results of CI engine must differ from that of petrol engine
due to much higher compression and expansion ratios in the former. The higher compression
ratio results in lower exhaust gas temperature and also lower flame temperature that in turn
causes lower heat loss to the cylinder walls in CI engines.
The utilization of the fuel’s heat energy is also higher in CI engines because of its higher
compression ratio.
Although the actual value of heat utilization is dependent upon a number of factors like
compression ratio, engine load, fuel injection quantity, timing etc. some average figures for heat

Item S.I. Engine C.I. Engine
Heat converted to useful work (i.p.) 25 to 32% 36 to 45%
Heat carried away by cooling water 33 to 30% 30 to 28%
Heat carried away by exhaust gases 35 to 28% 29 to 20%
Heat unaccounted for 7 to 10% 5 to 7%
Total (= Energy supplied) 100% 100%
balances for both the engines are given below :
If the shaft work (b.p.) is considered instead of useful work, the mechanical losses are to be
accounted for or are generally included in the cooling water heat.

An eight cylinder automobile petrol engine of bore 85.7 mm and stroke 82.5 mm
with a compression ratio of 7: 1 was tested on a dynamometer which has an arm of
533.5 mm long. The dynamometer scale reading was 400 N and the speed of the
engine was 4000 RPM. During the 10 minutes run fuel consumption was 4.55 kg.
The heating value of fuel was 45980 kJ/Kg. Quantity of air supplied through the
carburetor was 5.44 kg per minute at a pressure of 0.1 MPa and at a temperature of
293 K. Find the following: (a) The brake power developed, (b) The brake mean
effective pressure, (c) The brake specific fuel and air consumption (d) The brake
thermal efficiency (e) the volumetric efficiency. Gas constant for air is 287.14 J/kg-K.

Friday, 13 March 2015

Non-Traditional Manufacturing Processes (NTMP) Assignment - ElectroChemical Machining (ECM) - MRR




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Question: Prove that Volumetric Material Removal Rate (MRR) for an alloy with ‘n’ elements by Electrochemical Machining is given by: 1 MRR 100 n i i i i I F x M      where, xi is weight percent composition of ith element in the alloy, νi is the valency of ith element, Mi is the atomic weight of ith element in the alloy, ρ is the density of the material, F is the Faraday’s constant, I is the current in the machining process. (Hint: Use Faraday’s Laws) Solution: Electrochemical Machining is governed by Faraday’s laws. The first law states that the amount of electrochemical dissolution is proportional to amount of charge passed through the electrochemical cell, which may be expressed as: m  Q The second law states that the amount of material deposited or dissolved proportional to the Electrochemical Equivalence (ECE) of the material. Thus, m ECE A    m QA ItA m ItA F         where, F = Faraday’s constant Now, MRR m t MRR IA F      Now for passing a current of I for a time t, the mass of material dissolved for any element ‘i’ is given by 100 a i i m x    where Γa is the total volume of alloy dissolved. 100 i i i i i i i i a i i i i m QM F Q F m M Q F x M           1 1 1 1 1 1 100 100 100 Now, 100 100 n T i i n n a i i i i T a i i i i a n i i i i a n i i a i i n i i i i Q It Q Q It F x F x M M It F x M MRR t It F x MRR M t t MRR I F x M                                       

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Assignment: (Dead Line – 13th March 2015) Question: Prove that Volumetric Material Removal Rate (MRR) for an alloy with ‘n’ elements by Electrochemical Machining is given by: 1 MRR 100 n i i i i I F x M      where, xi is weight percent composition of ith element in the alloy, νi is the valency of ith element, Mi is the atomic weight of ith element in the alloy, ρ is the density of the material, F is the Faraday’s constant, I is the current in the machining process. (Hint: Use Faraday’s Laws) Solution: Volumetric Material removal rate (MRR) is the volume of material removed from the job material per unit time during the machining. In ECM, material removal takes place due to atomic dissolution of work material. Electrochemical dissolution is governed by Faraday’s laws of electrolysis. The first law states that the amount of chemical change i.e., the amount of electrochemical dissolution or deposition is proportional to amount of charge passed through the electrochemical cell that is again the product of current and the time passed, which may be expressed as: m  Q  It …. eqn (1) where m = mass of material dissolved or deposited; and Q = amount of charge passed The second law states that the amount of material deposited or dissolved further depends on Electrochemical Equivalence (ECE) of the material that is again the ratio atomic weight (M) and valency (ν). Thus, m ECE M    …. eqn (2) From equations (1) & (2), we have, m ItM m ItM F      where, F = Faraday’s constant = 96500 coulombs Now, Volume removed / Time taken MRR m m t t ItM MRR F IM t F MRR IM F                     where, I = current, ρ = density of the material Let us assume there are ‘n’ elements in an alloy. The atomic weights are given as Mi (M1, M2,…Mn) with valency during electrochemical dissolution as νi (ν1, ν2,…νn). The weight percentages of different elements are xi (x1, x2,…xn). Now for passing a current of I for a time t, the mass of material dissolved for any element ‘i’ is given by 100 a i i m V x   where Va is the total volume of alloy dissolved. Each element present in the alloy takes a certain amount of charge to dissolve.  /100 100 i i i i i i i i i a i i i a i i i i m QM F Q F m M F V x Q M Q FV x M              The total charge (QT) passed is the algebraic sum of charge passed of individual elements in the alloy. So, we can write, 1 1 1 1 1 1 1 100 100 100 100 Now, Total volume dissolved Total time 100 100 100 n T i i n n a i i i i T a i i i i n i i a i i a n i i i i a n i i a i i n i i i i Q It Q Q It FV x V F x M M It V F x M V It F x M MRR V t It F x MRR V M I t t F x M MRR                                             1 n i i i i I F x M     Thus, Volumetric Material Removal Rate (MRR) for an alloy with ‘n’ elements by Electrochemical Machining is given by: 1 MRR 100 n i i i i I F x M     
Module 9 Non conventional Machining Version 2 ME, IIT Kharagpur Lesson 38 Electro Chemical Machining Version 2 ME, IIT Kharagpur Instructional Objectives (i) Identify electro-chemical machining (ECM) as a particular type of non-tradition processes (ii) Describe the basic working principle of ECM process (iii) Draw schematically the basics of ECM (iv) Draw the tool potential drop (v) Describe material removal mechanism in ECM (vi) Identify the process parameters in ECM (vii) Develop models for material removal rate in ECM (viii) Analyse the dynamics of ECM process (ix) Identify different modules of ECM equipment (x) List four application of ECM (xi) Draw schematics of four such ECM applications 1. Introduction Electrochemical Machining (ECM) is a non-traditional machining (NTM) process belonging to Electrochemical category. ECM is opposite of electrochemical or galvanic coating or deposition process. Thus ECM can be thought of a controlled anodic dissolution at atomic level of the work piece that is electrically conductive by a shaped tool due to flow of high current at relatively low potential difference through an electrolyte which is quite often water based neutral salt solution. Fig. 1 schematically shows the basic principle of ECM. In ECM, the workpiece is connected to the positive terminal of a low voltage high current DC generator or power source. The tool is shaped and shape of the tool is transferred to the workpiece. The tool is connected to the negative terminal. Machining takes place due to anodic dissolution at atomic level of the work material due to electrochemical reaction. A gap between the tool and the workpiece is required to be maintained to proceed with steady state machining. W O R K T O O L WO R K T O O L electrolyte Fig. 1 Schematic principle of Electro Chemical Machining (ECM) 2. Process During ECM, there will be reactions occurring at the electrodes i.e. at the anode or workpiece and at the cathode or the tool along with within the electrolyte. Let us take an example of machining of low carbon steel which is primarily a ferrous alloy mainly containing iron. For electrochemical machining of steel, generally a neutral salt solution of sodium chloride (NaCl) is taken as the electrolyte. The electrolyte and water undergoes ionic dissociation as shown below as potential difference is applied NaCl ↔ Na+ + Cl- H2O H↔+ + (OH)- Version 2 ME, IIT Kharagpur As the potential difference is applied between the work piece (anode) and the tool (cathode), the positive ions move towards the tool and negative ions move towards the workpiece. Thus the hydrogen ions will take away electrons from the cathode (tool) and from hydrogen gas as: 2H+ + 2e- = H2↑ at cathode Similarly, the iron atoms will come out of the anode (work piece) as: Fe = Fe+ + + 2e- Within the electrolyte iron ions would combine with chloride ions to form iron chloride and similarly sodium ions would combine with hydroxyl ions to form sodium hydroxide Na+ + OH- = NaOH In practice FeCl2 and Fe(OH)2 would form and get precipitated in the form of sludge. In this manner it can be noted that the work piece gets gradually machined and gets precipitated as the sludge. Moreover there is not coating on the tool, only hydrogen gas evolves at the tool or cathode. Fig. 2 depicts the electro-chemical reactions schematically. As the material removal takes place due to atomic level dissociation, the machined surface is of excellent surface finish and stress free. W O R K T O O L Fe++ Fe++ OH−OH−OH−OH− Na+Na+Cl-Cl- H+H+OH−Fe++Fe(OH)2 FeCl2 e e H2 Fig. 2 Schematic representation of electro-chemical reactions The voltage is required to be applied for the electrochemical reaction to proceed at a steady state. That voltage or potential difference is around 2 to 30 V. The applied potential difference, however, also overcomes the following resistances or potential drops. They are: • The electrode potential • The activation over potential • Ohmic potential drop • Concentration over potential • Ohmic resistance of electrolyte Fig. 3 shows the total potential drop in ECM cell. Version 2 ME, IIT Kharagpur Anodic overvoltage Anode potential Activation over potential ohmic potential concentration potential concentration potential Ohmic drop activation overpotentialanode cathode cathodic potential cathodic overpotential Voltage Voltage Fig. 3 Total potential drop in ECM cell 3. Equipment The electrochemical machining system has the following modules: • Power supply • Electrolyte filtration and delivery system • Tool feed system • Working tank Fig. 4 schematically shows an electrochemical drilling unit. Flow control valve Pressure relief valve Pump Filters sludge centrifuge Spent electrolyte Tool Flow meter Pressure gauge Constant feed to the tool Low voltage high current power supply +ve -ve PS O M M O P Fig. 4 Schematic diagram of an electrochemical drilling unit Version 2 ME, IIT Kharagpur 4. Modelling of material removal rate Material removal rate (MRR) is an important characteristic to evaluate efficiency of a non-traditional machining process. In ECM, material removal takes place due to atomic dissolution of work material. Electrochemical dissolution is governed by Faraday’s laws. The first law states that the amount of electrochemical dissolution or deposition is proportional to amount of charge passed through the electrochemical cell, which may be expressed as: mQ∝, where m = mass of material dissolved or deposited Q = amount of charge passed The second law states that the amount of material deposited or dissolved further depends on Electrochemical Equivalence (ECE) of the material that is again the ratio atomic weigh and valency. Thus of thet νααAECEm Thus ναQAm where F = Faraday’s constant = 96500 coulombs νFItAm=∴ ρνρFIAtmMRR==∴ where I = current ρ= density of the material The engineering materials are quite often alloys rather than element consisting of different elements in a given proportion. Let us assume there are ‘n’ elements in an alloy. The atomic weights are given as A1, A2, ………….., An with valency during electrochemical dissolution as ν1, ν2, …………, νn. The weight percentages of different elements are α1, α2, ………….., αn (in decimal fraction) Now for passing a current of I for a time t, the mass of material dissolved for any element ‘i’ is given by iaimραΓ= where Γa is the total volume of alloy dissolved. Each element present in the alloy takes a certain amount of charge to dissolve. iiiiFAQmν= iiiiAFmQν=⇒ iiiaiAFQνραΓ=⇒ The total charge passed Version 2 ME, IIT Kharagpur Σ==iTQItQ Σ==∴iiiaTAFItQναρΓ Now Σ=Γ=iia IFtMRRναρ.1 5. Dynamics of Electrochemical Machining ECM can be undertaken without any feed to the tool or with a feed to the tool so that a steady machining gap is maintained. Let us first analyse the dynamics with NO FEED to the tool. Fig. 5 schematically shows the machining (ECM) with no feed to the tool and an instantaneous gap between the tool and workpiece of ‘h’. job electrolyte tool dh h Fig. 5 Schematic representation of the ECM process with no feed to the tool Now over a small time period ‘dt’ a current of I is passed through the electrolyte and that leads to a electrochemical dissolution of the material of amount ‘dh’ over an area of S rhVssrhVRVI===∴ then ⎟⎠⎞⎜⎝⎛=s1.rhVsA.F1dtdhxxρν Version 2 ME, IIT Kharagpur rhV.A.F1xxρν= for a given potential difference and alloy hch1.rFVAdtdhxx==ρν where c = constant rFVAxxρν= Σ=iiiArFVcναρ hcdtdh=∴ cdthdh= At t = 0, h = ho and at t = t1 and h = h1 ∫∫=∴1hoht0dtchdh ct2hh2o21=−∴ That is the tool – workpiece gap under zero feed condition grows gradually following a parabolic curve as shown in Fig. 6 h t ho Fig. 6 Variation of tool-workpiece gap under zero feed condition As hcdtdh= Thus dissolution would gradually decrease with increase in gap as the potential drop across the electrolyte would increase Version 2 ME, IIT Kharagpur Now generally in ECM a feed (f) is given to the tool fhcdtdh−=∴ Now if the feed rate is high as compared to rate of dissolution, then after sometime the gap would diminish and may even lead to short circuiting. Under steady state condition the gap is uniform i.e. the approach of the tool is compensated by dissolution of the work material. Thus with respect to the tool, the workpiece is not moving Thus fhc0dtdh=== hcf=∴ or h* = steady state gap = c/f Now under practical ECM condition it is not possible to set exactly the value of h* as the initial gap. Thus it is required to be analysed if the initial gap value would have any effect on progress of the process Now fhcdtdh−= Now chf*hh'h== And ctf*hft't2== dtdh.f1dtdh.c/fc/f'dt'dh2==∴ Thus fhcdtdh−= fc'hcff*h'hc'dt'dhf−=−=⇒ ⎟⎠⎞⎜⎝⎛−=⇒'h'h1f'dt'dhf 'h'h1'dt'dh−=⇒ 'dh'h1'h'dt−=∴ Now integrating between t’ = 0 to t’ = t’ when h’ changes from ho’ to h1’ 'dh'h1'h'dt't0'1h'oh∫∫−=∴ ()()()∫−+∫−−−=∴'1h'oh'1h'oh'h1d'h1'h1d't 1h1hlnhh't'1'o'1'o−−+−= now for different value of ho’, h1’ seems to approach 1 as shown in Fig. 7 Version 2 ME, IIT Kharagpur h1' t' h0= 0 h0= 0.5 1 Simulation for ho'= 0, 0.5, 1, 2, 3, 4, 5 Fig. 7 Variation in steady state gap with time for different initial gap Thus irrespective of initial gap 1cfh1*hh'h=⇒== fch=∴ or h1.rFVAhcfxxρν== si.FArhV.FAfxxxxρνρν==∴ s/mminMRRsI.FAfxx==∴ρν Thus it seems from the above equation that ECM is self regulating as MRR is equal to feed rate. 6. Applications ECM technique removes material by atomic level dissolution of the same by electrochemical action. Thus the material removal rate or machining is not dependent on the mechanical or physical properties of the work material. It only depends on the atomic weight and valency of the work material and the condition that it should be electrically conductive. Thus ECM can machine any electrically conductive work material irrespective of their hardness, strength or even thermal properties. Moreover Version 2 ME, IIT Kharagpur as ECM leads to atomic level dissolution, the surface finish is excellent with almost stress free machined surface and without any thermal damage. ECM is used for • Die sinking • Profiling and contouring • Trepanning • Grinding • Drilling • Micro-machining Die sinking 3D profiling Work Tool Fig. 8 Different applications of Electro Chemical Machining drilling (drilling) work tool Version 2 ME, IIT Kharagpur trepanning toolwork Fig. 9 Drilling and Trepanning by ECM 7. Process Parameters Power Supply Type direct current Voltage 2 to 35 V Current 50 to 40,000 A Current density 0.1 A/mm2 to 5 A/mm2 Electrolyte Material NaCl and NaNO3 Temperature 20oC – 50oC Flow rate 20 lpm per 100 A current Pressure 0.5 to 20 bar Dilution 100 g/l to 500 g/l Working gap 0.1 mm to 2 mm Overcut 0.2 mm to 3 mm Feed rate 0.5 mm/min to 15 mm/min Electrode material Copper, brass, bronze Surface roughness, Ra 0.2 to 1.5 μm Version 2 ME, IIT Kharagpur Quiz Test 1. For ECM of steel which is used as the electrolyte (a) kerosene (b) NaCl (c) Deionised water (d) HNO3 2. MRR in ECM depends on (a) Hardness of work material (b) atomic weight of work material (c) thermal conductivity of work material (d) ductility of work material 3. ECM cannot be undertaken for (a) steel (b) Nickel based superalloy (c) Al2O3 (d) Titanium alloy 4. Commercial ECM is carried out at a combination of (a) low voltage high current (b) low current low voltage (c) high current high voltage (d) low current low voltage Problems 1. In electrochemical machining of pure iron a material removal rate of 600 mm3/min is required. Estimate current requirement. 2. Composition of a Nickel superalloy is as follows: Ni = 70.0%, Cr = 20.0%, Fe = 5.0% and rest Titanium Calculate rate of dissolution if the area of the tool is 1500 mm2 and a current of 2000 A is being passed through the cell. Assume dissolution to take place at lowest valency of the elements. ANi = 58.71 ρNi = 8.9 νNi = 2 ACr = 51.99 ρCr = 7.19 νCr = 2 AFe = 55.85 ρFe = 7.86 νFe = 2 ATi = 47.9 ρTi = 4.51 νTi = 3 3. In ECM operation of pure iron an equilibrium gap of 2 mm is to be kept. Determine supply voltage, if the total overvoltage is 2.5 V. The resistivity of the electrolyte is 50 Ω-mm and the set feed rate is 0.25 mm/min. Version 2 ME, IIT Kharagpur Answers Answers to Quiz Test 1 – (b) 2 – (b) 3 – (c) 4 – (a) Solution to Prob. 1 νFAItmmMRR.=== ρνρΓFAItmMRR.===∴ MRR = 600 mm3/min = 600/60 mm3/s = 10 mm3/s = 10x10-3cc/s 2x8.7x96500xI5610x103=∴− As AFe = 56 νFe = 2 F = 96500 coulomb ρ = 7.8 gm/cc 562x8.7x10x10x96500I3−=∴ I = 268.8 A Answer Solution of Problem 2 Now, Σ=iialloy1ραρ TiTiFeFeCrCrNiNi1ραραραρα+++= cc/gm07.851.405.086.705.019.72.09.87.01=+++= Now Σ==iiiAFItmMRRναρρ ⎭⎬⎫⎩⎨⎧+++=9.473x05.085.552x05.099.512x2.071.582x75.0x07.8x965001000 = 0.0356 cc/sec = 2.14 cc/min = 2140 mm3/min Version 2 ME, IIT Kharagpur min/mm43.115002140AreaMRRndissolutioofRate===∴ answer Solution to Prob. 3 fc*h= where FeFeFerFVAcνρ= ()2x50x10x8.7x9650085.55x5.2VC3−−= ()7.13475.2V−= ()6025.0x13475.2Vfc2*h−=== 615.55.2V2−= .Volt73.8V=∴ Answer Version 2 ME, IIT Kharagpur

Friday, 19 December 2014

Cocubes - Employability Aptitude Test 2015 - (August 2014) at IIT Kharagpur

This is the Cocubes - Employability Aptitude Test 2015 - (August 2014) at IIT Kharagpur.

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Cocubes - Employability Aptitude Test 2015 ID Questions Question Image 1 In a PQR, the internal bisectors of the angles P, Q and R intersect the circumcircle of PQR at X, Y and Z respectively. If angle P measures 50 degrees, angle RZY measures 30 degrees, then angle QYZ will be:________________ A. 45 degrees B. 55 degrees C. 35 degrees D. 30 degrees 2 Side WX of rectangle of WXYZ is divided into four equal parts by points P, Q and R. The ratio of the area of PQY to the area of rectangle WXYZ is:________________ A. 1/7 B. 1/6 C. 1/8 D. 1/16 3 How many quadrilaterals can be formed by joining the vertices of an octagon?________________ A. 40 B. 50 C. 70 D. 20 4 Answer the questions 4 & 5 on the basis of the information given below. The following pie chart provides information about the marks obtained by six students A, B, C, D, E and F, in four different subjects P, Q, R and S. The marks obtained by each of the students in subject P is indexed to the maximum marks that can be obtained in subject P. This holds true for the other three subjects as well. For example, if the maximum marks that can be obtained in subject P is ' 40k ', then the marks obtained in subject P by student A is 15k, by student B is 20k and so on. This holds true for the marks obtained by the students in the other three subjects as well. The marks obtained by A in subject P is not less than that obtained by him in subject Q or subject R, but not more than that obtained by him in subject S. This holds true for the marks obtained by each of the other 5 students as well. If the marks obtained by A in subjects Q and R is the same, then the maximum marks that can be obtained in subject Q as a percentage of the maximum marks that can be obtained in subject R is: (click on image to zoom it)________________ A. 50/3 B. 250/3 C. 100/3 D. 20 5 Answer the questions 4 & 5 on the basis of the information given below. The following pie chart provides information about the marks obtained by six students A, B, C, D, E and F, in four different subjects P, Q, R and S. The marks obtained by each of the students in subject P is indexed to the maximum marks that can be obtained in subject P. This holds true for the other three subjects as well. For example, if the maximum marks that can be obtained in subject P is ' 40k ', then the marks obtained in subject P by student A is 15k, by student B is 20k and so on. This holds true for the marks obtained by the students in the other three subjects as well. The marks obtained by A in subject P is not less than that obtained by him in subject Q or subject R, but not more than that obtained by him in subject S. This holds true for the marks obtained by each of the other 5 students as well. A student is said to have passed a given subject, if and only if he has obtained at least 40% of the maximum marks that can be obtained in that subject. In how many of the subjects at least three of the students have passed? (click on image to zoom it)________________ A. 2 B. 0 C. 1 D. 3 6 A 20 litre mixture of milk and water contains milk and water in the ratio of 3 : 2. 10 litres of the mixture is replaced with pure milk in the vessel and then this operation is repeated once more. At the end of the two replacements, what would be the ratio of milk and water in the resultant mixture?________________ A. 17 : 3 B. 1 : 9 C. 9 : 1 D. 5 : 3 7 Pipe X fills a tank of 700 litres capacity at a rate of 40 litres a minute. Another pipe Y, fills the same tank at a rate of 30 litres a minute. A pipe Z, at the bottom of the tank, drains the tank at a rate of 20 litres a minute. If pipe X is kept open for a minute and then closed and then pipe Y is kept open for a minute and then closed and then pipe Z is kept open for a minute and then closed and further, the cycle is being repeated till the tank overflows. How long will it take for the empty tank to overflow?________________ A. 20 min 10 sec B. 40 min 20 sec C. 22 min 15 sec D. 40 min 50 sec 8 A tempo, while travelling at 70 kmph, uses 30% more petrol than it uses while travelling at 50 kmph for travelling a certain distance. Using one litre of petrol, it can travel 19.5 km at 50 kmph. How far can the tempo travel on 10 litres of petrol at a speed of 70 kmph?________________ A. 130 km B. 140 km C. 150 km D. 160 km 9 If three times the larger of two numbers is divided by the smaller number, we get 4 as the quotient and 3 as the remainder. Also, if seven times the smaller number is divided by the larger one, we get 5 as quotient and 1 as the remainder. Find the difference between these numbers.________________ A. 7 B. 18 C. 25 D. 14 10 Read the information given below and answer the question: After the Ranji trophy series, 5 players were asked to stand in the increasing order of runs scored by them. Rajesh was fourth while Mahesh was first. When they were asked to stand in decreasing order of number of wickets taken by them, Inder replaced Rajesh while Rajesh replaced Mohan. Ravinder's position remained unchanged. It is known that Inder scored more runs than Ravinder. If Mohan's rank was first in one of the rankings and fifth in the other, who scored the highest runs in the series?________________ A. Inder B. Mohan C. Ravinder D. Cannot be determined 11 A train consists of 12 bogies, each bogie is 15 meters long. The train crosses a telegraph pole in 18 seconds. Due to some problem, two bogies were detached. How much time train would take now to cross a telegraph post?________________ A. 18 sec B. 12 sec C. 15 sec D. 20 sec 12 Two lumps of a mixture of gold, silver and copper together weigh 20 kg. One lump contains 75% gold and 31.25 g silver per kilogram. Another lump contains 85% gold and 30 g silver per kilogram. The total quantity of silver in two lumps is 617.5 gm. If two lumps are melted to form one, the percentage of gold in it will be:________________ A. 75 B. 87 C. 15.6 D. 78 13 If (x + 2) exactly divides x3 6x2 11x 6k  , find k.________________ A. 2 B. 1 C. 0 D. 4 14 A group of 10 army persons is to be sent on a mission. The group is to be selected from six men commanders and ten lieutenants comprising of 5 men lieutenants and 5 women lieutenants. In how many ways can this be done, if the group must have at least four commanders and at least four lieutenants with at least 2 men lieutenants and 2 women lieutenants?________________ A. 4300 B. 3700 C. 5100 D. 5000 15 Answer the following questions 15 & 16 on the basis of the information given below. Following things are true about the flats (100 in total) in the Royal Society: 1. There are 93 flats which have Wi-Fi connection. 2. There are 62 flats which have landline telephone. 3. There are 85 flats which have AC. What is the minimum number of flats that have all the three facilities?________________ A. 39 B. 40 C. 41 D. 42 16 Answer the following questions 15 & 16 on the basis of the information given below. Following things are true about the flats (100 in total) in the Royal Society: 1. There are 93 flats which have Wi-Fi connection. 2. There are 62 flats which have landline telephone. 3. There are 85 flats which have AC. What is the maximum number of flats having one or two facilities?________________ A. 60 B. 64 C. 63 D. 69 17 The denominator of a fraction is 3 more than the numerator. If 4 is added to both the numerator and the denominator, the fraction becomes 4/5. The fraction is:________________ A. 5/8 B. 10/13 C. 7/10 D. 8/11 18 Gautam sat for his NTSCE exam where every correct answer was awarded 3 marks and 1 mark was deducted for every wrong answer. His score was 40. Had he been awarded 4 marks for every correct answer and 2 marks would have been deducted for every wrong answer, his score would have been 50. How many questions were there in the paper if he attempted all the questions in the same manner in both the scenarios?________________ A. 20 B. 30 C. 40 D. 50 19 A and B are participating in a swimming race of 1000 m. Both of them start simultaneously at one end of a swimming pool whose length is 50 m. A beats B in the race and meets him 17 times during the course. If A's speed is 5 m/s then the speed of B could be (rounded off to nearest whole number):________________ A. 1 m/s B. 3 m/s C. 4 m/s D. 6 m/s 20 How many numbers of five digits can be formed with digits 1,3,5,7 & 9 with no digit being repeated in the same number?________________ A. 55 B. 120 C. 125 D. 15 21 In the question given below, a statement followed by some arguments is given. You have to decide which of the given arguments is/are a strong argument and which is/are weak. Mark the answer accordingly. Statement: Should the consumption of chicken be banned in India? Arguments: I. Yes, this is the only way to reduce the risk of exposing people to Swine Flu. II. No, each individual should have right to choose what he wants. III. No, there is no confirmed evidence that every cuisine made out of chicken can have adverse effect on human body. IV. Yes, it is banned in many other countries also.________________ A. Only I and II are strong B. All are strong C. Only III is strong D. Only I is strong 22 In the question given below, a statement followed by some arguments is given. You have to decide which of the given arguments is/are a strong argument and which is/are weak. Mark the answer accordingly. Statement: Should military training be made compulsory in our country like other countries? Arguments: I. Yes, every citizen has duty to protect his country. II. No, it is against the policy of nonviolence.________________ A. Both first and second arguments are strong. B. Neither first nor second argument is strong. C. Only second argument is strong. D. Either first or second argument is strong. 23 In the question given below, a statement followed by some arguments is given. You have to decide which of the given arguments is/are a strong argument and which is/are weak. Mark the answer accordingly. Statement: Should jobs be delinked with academic degrees and diplomas? Arguments: I. Yes, a very large number of candidates will apply so that the competition will be tough and the candidates will prepare more. II. No, importance of higher education will be diminished.________________ A. Only first argument is strong. B. Neither first nor second argument is strong. C. Only second argument is strong. D. Both first and second arguments are strong. 24 In the question given below, a statement followed by some arguments is given. You have to decide which of the given arguments is/are a strong argument and which is/are weak. Mark the answer accordingly. Statement: Should those who receive dowry be encouraged? Arguments: I. Yes, due to this, the number of those who receive dowry will decrease. II. No, due to this the number of those who receive dowry will increase.________________ A. Both first and second arguments are strong. B. Only first argument is strong. C. Only second argument is strong. D. Neither first nor second argument is strong. 25 What will be the value of i at the end of the flowchart if the input number is 7? ________________ A. 6 B. 7 C. 8 D. 9 26 If the decision "Is i > or = input number?" is replaced by "Is i = input number" then will the output of the flowchart change? ________________ A. No B. Yes C. Depends on the input number D. Can't Say 27 If the decision "Is i > or = input number?" is replaced by "Is i > input number" then will the output of the flowchart change? ________________ A. No B. Yes C. Depends on the input number D. Can't Say 28 In the following question, a square transparent sheet with a pattern is given. Choose the answer which shows how the pattern would appear when the transparent sheet is folded along the dotted line as shown by the arrow. Transparent Sheet: Response Sheet: ________________ A. (1) B. (2) C. (3) D. (4) 29 For the following question, choose the answer that best completes the comparison. 80 : 730 :: ? : 344________________ A. 48 B. 70 C. 40 D. 52 30 In the following question, three statements are given followed by four conclusions numbered I, II, III and IV. You have to take the given statements to be true even if they seem to be at variance with commonly known facts and then decide which of the given conclusions logically follows from the given statements disregarding commonly known facts. Statements: All pencils are pens. Some pens are sketch-pens. All sketch-pens are papers. Conclusions: I. Some papers are pencils. II. Some papers are pens. III. Some sketch-pens are pencils. IV. No paper is pencil.________________ A. None follows B. Either I or III follow C. Either I or II and IV follow D. All follow 31 In the following question, three statements are given followed by four conclusions numbered I, II, III and IV. You have to take the given statements to be true even if they seem to be at variance with commonly known facts and then decide which of the given conclusions logically follows from the given statements disregarding commonly known facts. Statements: All singers are actors. No doctor is singer. Some dancers are doctors. Conclusions: I. Some dancers are singers. II. Some actors are dancers. III. All doctors are dancers. IV. Some actors are doctors.________________ A. Only I and III follow B. All follow C. Only I and II follow D. None follows 32 Refer to the data given below and answer the questions 32 & 33 that follow. A 9-digit code is to be formed using 6 distinct numbers and 3 vowels. 1) Digit at the first place is square of prime number which is in the fourth place. 2) Digit at fifth, eighth, second and first places are consecutive numbers in the ascending order. 3) All odd digits except 1 are present in the code. 4) Vowels are placed at positions of the code which are first three multiples of three. The digit at the fifth place is:________________ A. 7 B. 6 C. 3 D. 5 33 Refer to the data given below and answer the questions 32 & 33 that follow. A 9-digit code is to be formed using 6 distinct numbers and 3 vowels. 1) Digit at the first place is square of prime number which is in the fourth place. 2) Digit at fifth, eighth, second and first places are consecutive numbers in the ascending order. 3) All odd digits except 1 are present in the code. 4) Vowels are placed at positions of the code which are first three multiples of three. The digit at the first place corresponds to the place which a vowel occupies in the alphabetical order; the vowel being placed at the extreme position in the code. Find the last 3 entities of the code.________________ A. 79a B. 67e C. 97i D. 57i 34 Refer to the data below and answer the questions 34 & 35 that follow. The 5 participants in a car race are Daric, Garry, Danny, Elviana and Erica. The starting point of the race is at 'A', the participants need to move 10 kms due East to reach point 'B', then drive for 8 kms due South east to reach point 'C'. Then make a clockwise semi-circular turn of 7 kms to reach point 'D' which is to the South of point 'C'. Then a 12 kms straight drive due West to reach the finishing point 'E'. Also consider the following information about speed of the candidates. * Daric is twice as fast as Danny. * Erica and Danny drive at same speeds. If Erica has covered 6 kms, in which direction is Daric headed?________________ A. East B. West C. South east D. Cannot be determined 35 Refer to the data below and answer the questions 34 & 35 that follow. The 5 participants in a car race are Daric, Garry, Danny, Elviana and Erica. The starting point of the race is at 'A', the participants need to move 10 kms due East to reach point 'B', then drive for 8 kms due South east to reach point 'C'. Then make a clockwise semi-circular turn of 7 kms to reach point 'D' which is to the South of point 'C'. Then a 12 kms straight drive due West to reach the finishing point 'E'. Also consider the following information about speed of the candidates. * Daric is twice as fast as Danny. * Erica and Danny drive at same speeds. If Garry is 3 kms behind Daric, which direction does he need to take next? (Use data from previous question)________________ A. West B. East C. South east D. South 36 Answer the following question based on the statements given below. Does he go to office every day? Statements: I. He is never defamed for absence. II. He is never at his home during office hours.________________ A. Only 1 of the statements is sufficient to answer the given question but the other statement is not. B. Both statements I and II together are sufficient to answer the question although neither of the statements alone suffices. C. Each statement, individually, is sufficient to answer the question. D. Both statements I and II together are not sufficient to answer the question asked, and additional data to the problem are needed. 37 Answer the following question based on the statements given below. Are all footballs basketballs? Statements: I. All animals are footballs II. All basketballs are animals________________ A. Only 1 of the statements is sufficient to answer the given question but the other statement is not. B. Both statements I and II together are sufficient to answer the question although neither of the statements alone suffices. C. Each statement, individually, is sufficient to answer the question. D. Both statements I and II together are not sufficient to answer the question asked, and additional data to the problem are needed. 38 Question: How is 'FATE' written in the code language? Statements: I. FEAR is written as PQRS in that code. II. TREAT is written as LMQRS in that code. III. TEAR is written as LQRS in that code.________________ A. Statement I, II and III are required to answer the question asked. B. Only I and either II or III are required to answer the question asked. C. Only I and II are required to answer the question asked. D. None of these statements is sufficient to answer the question asked. 39 Question: How many daughters does F have? Statements: I. P and S are sisters of M. II. R is brother of J and S. III. R and M are sons of F.________________ A. Only statement II and III are required to answer the question asked. B. Statement I, II and III are required to answer the question asked. C. Only statement II is required to answer the question asked. D. None of these statements is sufficient to answer the question asked. 40 Three images from the following figure follow a similar pattern and one does not. Mark your answer as that image. ________________ A. (1) B. (2) C. (3) D. (4) 41 Consider the following given four choices and identify the odd one out.________________ A. Rubric B. Stricture C. Label D. Caption 42 Choose the most logical order of sentences from the given choices to construct a coherent paragraph. 1. The credit rating agencies use legions of high trained analyst with access to top management. 2. Their meticulous reports giving ratings for corporate bonds are designed to give an accurate picture of the bonds riskiness and ultimately the probability of default. 3. Lately, the credit-rating agencies have struggled to keep up. 4. It seems a bond rating tells you even less about the price that investors are willing to pay. 5. In 1999 two-third of the debt rated triple B by standard and poor was priced within 20 basis points of the average bond with the same rating.________________ A. 45123 B. 34215 C. 12345 D. 23415 43 In the following question, four similar sentences are given, of which only one is grammatically correct, stylistically elegant and semantically consistent. Identify that sentence.________________ A. His initial impression was that work was light and the compensation beautiful, but soon he realized that the pay was not commensurate with his role and responsibilities. B. His initial impression was that work was lighter and the compensation handsome, but soon he realized that the pay was not commensurate with his role and responsibilities. C. His initial impression was that work was light and the compensation handsome, but soon he realized that the pay was not commensurate with his role and responsibilities. D. His initial impression was that work was light and the compensation handsome, soon he realized that the pay was not commensurate with his role and responsibilities. 44 Fill in the blank(s) with the most suitable option. During the ________election week in May last year, _______politicians were busy dodging the issue of incomplete work they had done in the previous five years while promising a lot to the poor.________________ A. final, terse B. tumultuous, unscrupulous C. pitched, ineffective D. showy, unseasonable 45 Fill in the blank(s) with the most suitable option. My mother always detests _______ with shady children.________________ A. for dealing B. dealing C. to deal D. deals 46 Two of the four words given below have the same meaning, spot them. 1.CHOLERIC 2.INEPT 3.IRASCIBLE 4.INDENTATION________________ A. 1, 4 B. 1, 3 C. 3, 4 D. 1, 2 47 Choose the option which gives the closest meaning to the idiom. Baker's Dozen.________________ A. 12 items B. 13 items C. 14 items D. 15 items 48 Choose the most logical order of sentences among the given choices to construct a coherent paragraph. 1. Despite posting healthy profits, Volkswagen shares trade at a discount to peers due to bad reputation among investors. 2. A disastrous capital hike, an expensive foray into truck business and uncertainty about the reason for a share buyback have in recent years left investors bewildered. 3. The main problem with Volkswagen is the past. 4. Many investors have been disappointed and frightened away. 5. Volkswagen shares trade at about nine times the 2002 estimated earnings compared to BMW's 19 and are the second cheapest in the sector.________________ A. 52134 B. 13425 C. 32451 D. 13524 49 Identify the pair in which words are related to each other in the same way as the two CAPITALIZED words are, below. HIATUS : GAP________________ A. Imbecile : Smart B. Greenfield : Project C. Zenith : Pinnacle D. Nuptial : Cornucopia 50 Read the passage given below and answer the questions 50-52: Eco-efficiency (measures to minimize environmental impact through the reduction or elimination of waste from production processes) has become a goal for companies worldwide, with many realizing significant cost savings from such innovation. Peter Senge and Goran Carlstadt see this development as laudable but suggest that simply adopting eco-efficiency innovations could actually worsen environmental stresses in the future, such innovations reduce production waste but do not alter the number of products manufactured nor the waste companies invest in eco-efficiency improvements in order to increase profits and growth. Moreover, there is no guarantee the increased economic growth from eco-efficiency will come in similarly ecoefficient ways, since in today's global markets, greater profits may be turned into investment capital that could easily be reinvested in old style eco-inefficient industries. Even a vastly more eco-efficient industrial system could, were it to grow much larger, generate more total waste and destroy more habitat and species than would a smaller, less eco-efficient economy. Senge and Carlstadt argue that to preserve the global environment and sustain economic growth, businesses must develop a new systematic approach that reduces total material use and total accumulated waste. Focusing exclusively on eco-efficiency, (which offers a compelling business case according to established thinking) may distract companies from pursuing radically different products and business models. The primary purpose of the passage is to:________________ A. Explain why a particular business strategy has been less successful than was once anticipated. B. Propose an alternative to a particular business strategy that has inadvertently caused ecological damage. C. Present a concern about the possible consequences of pursuing a particular business strategy. D. Make a case for applying a particular business strategy on a large scale than is currently practiced. 51 Read the passage given below and answer the questions 50-52: Eco-efficiency (measures to minimize environmental impact through the reduction or elimination of waste from production processes) has become a goal for companies worldwide, with many realizing significant cost savings from such innovation. Peter Senge and Goran Carlstadt see this development as laudable but suggest that simply adopting eco-efficiency innovations could actually worsen environmental stresses in the future, such innovations reduce production waste but do not alter the number of products manufactured nor the waste companies invest in eco-efficiency improvements in order to increase profits and growth. Moreover, there is no guarantee the increased economic growth from eco-efficiency will come in similarly ecoefficient ways, since in today's global markets, greater profits may be turned into investment capital that could easily be reinvested in old style eco-inefficient industries. Even a vastly more eco-efficient industrial system could, were it to grow much larger, generate more total waste and destroy more habitat and species than would a smaller, less eco-efficient economy. Senge and Carlstadt argue that to preserve the global environment and sustain economic growth, businesses must develop a new systematic approach that reduces total material use and total accumulated waste. Focusing exclusively on eco-efficiency, (which offers a compelling business case according to established thinking) may distract companies from pursuing radically different products and business models. The passage mentions which of the following as a possible consequence of companies' realization of greater profits through ecoefficiency?________________ A. The companies may be able to sell a greater number of products by lowering prices. B. The companies may be better be reinvested to increase economic growth through eco-efficiency. C. The profits may be used as investment capital for industries that are not eco-efficient. D. The profits may encourage companies to make further innovations in reducing production waste. 52 Read the passage given below and answer the questions 50-52: Eco-efficiency (measures to minimize environmental impact through the reduction or elimination of waste from production processes) has become a goal for companies worldwide, with many realizing significant cost savings from such innovation. Peter Senge and Goran Carlstadt see this development as laudable but suggest that simply adopting eco-efficiency innovations could actually worsen environmental stresses in the future, such innovations reduce production waste but do not alter the number of products manufactured nor the waste companies invest in eco-efficiency improvements in order to increase profits and growth. Moreover, there is no guarantee the increased economic growth from eco-efficiency will come in similarly ecoefficient ways, since in today's global markets, greater profits may be turned into investment capital that could easily be reinvested in old style eco-inefficient industries. Even a vastly more eco-efficient industrial system could, were it to grow much larger, generate more total waste and destroy more habitat and species than would a smaller, less eco-efficient economy. Senge and Carlstadt argue that to preserve the global environment and sustain economic growth, businesses must develop a new systematic approach that reduces total material use and total accumulated waste. Focusing exclusively on eco-efficiency, (which offers a compelling business case according to established thinking) may distract companies from pursuing radically different products and business models. The passage implies that which of the following is a possible consequence of a company's adoption of innovations that increase its ecoefficiency?________________ A. Company profits resulting from such innovations may be reinvested in that company with no guarantee that the company will continue to make further improvements in eco-efficiency. B. Company growth fostered by cost savings from such innovations may allow that company to manufacture a greater number of products that will be used and discarded, thus worsening environmental stress. C. A company that fails to realize significant cost savings from such innovations may have little incentive to continue to minimize the environment impact of its production processes. D. A company that meets its eco-efficiency goals is unlikely to invest its increased profits in the development of new and innovative eco-efficiency measures. 53 Consider the following given four choices and identify the odd one out.________________ A. Profligacy B. Extravagance C. Embellishment D. Lavishness 54 One among the four given sets contains one or more words incorrectly spelled. Choose that set.________________ A. Aberration, Beleaguer, Belligerence, Cannoneer B. Cantankerous, Calisthenics, Boysenberry, Apocalypse C. Aficionado, Calisthenics, Cantankerous, Catastrophe D. Callous, Cardiopulmanary, Carnivorus, Camouflage 55 Read the passage below and answer the questions 55-57: My father died twice. The first time was in an ambulance when he was rushed to hospital after suffering a heart attack. His heart had stopped beating for several minutes before the paramedics were able to revive him. Afterwards, he described a vision he had as he lay without a pulse in the speeding ambulance. He saw his brother Joe, who had passed away some years earlier, dressed in flowing white robe sitting on a silver chair on top of a hill. As my father went close, Joe waved and asked him to return. The second time my father died was about three years later. Again it was heart that failed him. This time tough, his brother Joe wasn't there to wave him back to this world. The whole incident in the passage can be described as:________________ A. Superstition B. Reincarnation C. Rebirth D. Illusion 56 Read the passage below and answer the questions 55-57: My father died twice. The first time was in an ambulance when he was rushed to hospital after suffering a heart attack. His heart had stopped beating for several minutes before the paramedics were able to revive him. Afterwards, he described a vision he had as he lay without a pulse in the speeding ambulance. He saw his brother Joe, who had passed away some years earlier, dressed in flowing white robe sitting on a silver chair on top of a hill. As my father went close, Joe waved and asked him to return. The second time my father died was about three years later. Again it was heart that failed him. This time tough, his brother Joe wasn't there to wave him back to this world. What can be true about the father of the author?________________ A. He might be suffering from incurable disease. B. He might be having an artery blockage in heart. C. His brother Joe waived him good bye before putting in ambulance. D. His son was not with him at time of death. 57 Read the passage below and answer the questions 55-57: My father died twice. The first time was in an ambulance when he was rushed to hospital after suffering a heart attack. His heart had stopped beating for several minutes before the paramedics were able to revive him. Afterwards, he described a vision he had as he lay without a pulse in the speeding ambulance. He saw his brother Joe, who had passed away some years earlier, dressed in flowing white robe sitting on a silver chair on top of a hill. As my father went close, Joe waved and asked him to return. The second time my father died was about three years later. Again it was heart that failed him. This time tough, his brother Joe wasn't there to wave him back to this world. Which statement can be true about Joe?________________ A. Joe died of heart attack and after his brother's first death experience. B. Joe was in ambulance with his brother to waive him goodbye last time. C. Joe did not come to say goodbye to his dying brother. D. Joe was present only first time but not second. 58 Fill in the blank(s) with the most suitable option. In the long run, drinking proved fatal both ________ his reputation & health.________________ A. for B. to C. of D. None of these 59 Choose the best option from those given below to replace the underlined portion of the sentence: In the normal course of event, my son will graduate law school with a degree in law and he will join court in three years.________________ A. my son will graduate law school with a degree in law, he will join court in three years. B. my son will have graduated from law school with a degree in law and joined court in three years. C. my son will graduate from law school with degree in law, he will join court in three years. D. my son graduates law college with a degree in law and will join court in three years. 60 Choose the best option from those given below to replace the underlined portion of the sentence: The fact that the terrorists left no pamphlets has laid credence to the apprehension in certain quarters that it may have been orchestrated to discredit the security forces.________________ A. has layed credence to the apprehension B. was laid credence to the apprehension C. had laid credence to the apprehension D. has lent credence to the apprehension


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Cocubes conducts employability test in IIT Kharagpur for final campus placements.
This is the test conducted by CoCubes in 2014.

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Highest Score:60.00
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Friday, 25 July 2014

Design Of Machine Elements (ME30602) - Class test Question Bank with answers

INDIAN INSTITUTE OF TECHNOLOGY, KHARAGPUR
End/Mid Semester Examination
DESIGN OF MACHINE ELEMENTS
ME30602

Class Test
1. Answer all questions. All questions carry equal marks
2. Make suitable assumptions wherever necessary
3. Put √ on your chosen answer.
4. Any data, if not furnished, may be assumed.




1.     A new model of a car is a typical example of
a)     Adaptive design
b)    Developmental design
c) New design
2.     Adaptive design is based on
a)     Existing design adapted for new application
b)    New inventions for new application
c)     Conceptual design for new application
d)    New Technology for new application

3.     Which of the following design is based on based on experience and experiments?
a)     Rational design
b)    Empirical design
c)     Industrial design


4.     Use of factor of safety in designing the elements is to
a)     optimize the design to avoid over-design for reliability
b)    prevent loss of material and premature failure
c)     have good aesthetics of the designed product
d)    increase efficiency of the element

5.     A stainless steel is described as 18/8 steel. This indicates that it contains:
a)     8% Nickel and 18% Chromium
b)    18% Nickel and 8% Chromium
c)     18% Chromium and 8% Silicon
d)    8% Chromium and 18% Silicon

6.     Resilience is
a)     the property of the material that enables it to resist shock and impact by storing energy
b)    the property of the material that enables it to be twisted, bent or stretched under impact load or high stress before rupture
c)     the property of the material that enables it to be drawn out or elongated to an appreciable extent before rupture
d)    the property of the material that enables it to resist permanent deformation, penetration, indentation

7.     Resilience is the property of a material:
a)     that enables it to resist indentation
b)    that enables it to resist wear
c)     that enables it to resist shock and impact
d)    that enables it to resist scratching

8.     A standard alloy steel used for making engineering components is 20Cr18Ni2. The composition of this steel is:
a)     20% carbon, 18% chromium and 2% nickel
b)    0.2% chromium, 18% nickel and 2% carbon
c)     0.2% carbon, 18% chromium and 2% nickel
d)    20% chromium, 18% nickel and 2% carbon

9.     The composition of 20Cr18Ni2 is:
a)     20% Cr, 18%Ni, 2%Carbon
b)    0.2% carbon, 18% chromium and 2% nickel
c)     2% Cr, 0.18%Ni, 0.2%Carbon
d)    2% carbon, 0.18% chromium and 0.2% nickel

10.                        Allowance of a shaft-hole system is the difference between
a)     maximum dimension of shaft and minimum dimension of hole
b)    maximum dimension of shaft and maximum dimension of hole
c)     minimum dimension of shaft and minimum dimension of hole
d)    minimum dimension of shaft and maximum dimension of hole

11.                         Tolerance is the difference between:
a)     Maximum and minimum dimensions of a component
b)    Maximum dimension of the shaft and maximum dimensions of the hole
c)     Minimum and minimum dimensions of a component
d)    Minimum dimension of the shaft and the maximum dimension of the hole

12.                        In a unilateral system of tolerance, the tolerance is allowed on
a)     one side of the actual size
b)    one side of the nominal size
c)     both sides of the actual size
d)    both sides of the nominal size

13.                        Nominal size of a hole and shaft is 40 mm, the tolerance grade for making the hole is IT6 and for shaft is IT5. The fundamental deviation of shaft basis is positive and for hole is zero. Which of the following designation suits the above hole-shaft system?
a)     40M6/h5
b)    40M5/h6
c)     40H5/m6
d)    40H6/m5

14.                        Which of the following standard series is used for Capacities of hydraulic cylinder?
a)     R5
b)    R10
c)     R20
d)    R40

15.                         What is the bearing stress developed at the faces of a rectangular key fixing a gear hub on a shaft acted upon by a torque T as shown in figure?
                                                                                                       



16.                         Let the cross-sectional area of the plate, the larger hole H1 and the smaller holes H2 be A, a1, a2 respectively. If 2a2 > a1 , the critical section in the loaded plate is:

a)     A-A
b)    B-B
c)     C-C
d)    D-D




17.                         A 3m long cantilever beam of solid rectangular cross-section of 100mm width and 150mm depth is subjected to an end loading P as shown in the figure. If the allowable shear stress in the beam is 150 MPa, the safe value of P based on shear alone is

a)     1 MN
b)    1.5 MN
c)     2.3 MN
d)    3.5 MN


18.                         A vertical load Py = 20 kN is applied at the free end of a cylindrical bar of radius 50 mm as shown in figure. The principal stress at the point A is


a)     56MPa, 7.4MPa
b)    84MPa, −8.9MPa
c)     105MPa, 9.3MPa
d)    112.5MPa, −14.72MPa


19.                         An axially loaded brass (Ebrass = 90GPa) strut hinged at both ends is 1m long and is of a square cross-section of sides 20mm. The dimension of steel (Esteel = 200 GPa) strut of the same length and subjected to the same axial loads is:
a)     24.40 mm
b)    13.42 mm
c)     16.38 mm
d)    32.62 mm


20.                         The theoretical stress concentration factor at hole in a plate with transverse elliptical hole and subjected to a tensile load as shown in figure is:

                                                                                                             




21.                         Notch sensitivity factor, q is
                                                                                                     




22.                         The endurance or fatigue limit is defined as the maximum value of the stress which a polished standard specimen can withstand without failure, for infinite number of cycles, when subjected to
a)     static load
b)    dynamic load
c)     static as well as dynamic load
d)    completely reversed load


23.                         In the plate shown below it is required that the stress concentration at hole does not exceed that at the fillet. The hole diameter is

a)     21.5 mm
b)    35 mm
c)     41.9 mm
d)    53 mm
Data Provided:

24.                         Dowel pins are used for
a)     proper alignment
b)    loosening
c)     both for proper alignment and loosening


25.                         Dowel Pins are used
a)     To get a better grip
b)    To transmit torque smoothly
c)     For proper alignment


26.                         Studs are
a)     single headed fasteners
b)    double headed fasteners
c)     headless fasteners
d)    twin headed fasteners


27.                         A heat treated steel shaft of tensile yield strength of 350 MPa has a diameter of 50mm. The shaft rotates at 1000 rpm and transmits 100 kW through a gear. An appropriate key set of dimensions is:
a)     Width = 16 mm, Length = 45 mm, Depth = 10 mm
b)    Width = 10 mm, Length = 35 mm, Depth = 8 mm
c)     Width = 18 mm, Length = 55 mm, thickness = 11 mm
d)    Width = 20 mm, Length = 65 mm, thickness = 12 mm
Data Provided:
Shaft Diameter
(mm)
30-38
38-44
44-50
50-58
58-65
65-75
75-85
Key width, w
(mm)
10
12
14
16
18
20
22
Key depth, t
(mm)
8
9
9
10
11
12
14
Key length, L
(mm)
22-110
28-140
36-160
45-180
50-200
56-220
63-250




28.                         In a steam engine the steam pressure is 2 MPa and the cylinder diameter is 250 mm. The contact surfaces of the head and cylinder are ground and no packing is required. Assuming that the number of bolts to be used is 12, a suitable bolt for the joint to be leak proof would be:
a)     M20 x 1.5
b)    M16 x 1.5
c)     M5 x 0.8
d)    M10 x 1.25
Data provided:
Designation
Pitch
(mm)
Minor Diameter
Stress area
(mm2)
Bolt (mm)
Nut (mm)
M2
0.40
1.509
1.567
207
M5
0.8
4.019
4.134
14.2
M10
1.25
8.466
8.647
61.6
M16
1.5
14.160
14.376
167
M20
1.5
18.160
18.376
272
M24
2
21.546
21.835
384




29.                         Shear stress developed in the weld in the figure shown below is

a)     16.7 MPa
b)    21.9 MPa
c)     26.2 MPa


30.                         Considering unit weld width the polar moment of inertia of the weld group in above question is
a)     0.00365 m3
b)    0.000198 m3
c)     0.0000325 m3


31.                         If the yield strength of the weld material is 150MPa, the safe value of F is

a)     108 kN
b)    213 kN
c)     269 kN
d)    313 kN


32.                         In a triple riveted butt joint with two unequal straps 30 mm diameter rivets and 10mm plates (both main and straps) are used. The pitch at the outer row is 250mm. Considering that the joint fails only due to shearing of all the rivets and taking the working stresses to be σt = 75MPa, τy = 60MPa and σc = 130MPa, the joint efficiency is
a)     76.3%
b)    81.3%
c)     98.3%


33.                         Two plates of 7 mm thickness are connected by a double riveted lap joint of zigzag pattern. If the rivet diameter is 19mm and σt = 90MPa, σc = 120MPa, τ = 60 MPa, the rivet pitch is
a)     19 mm
b)    54 mm
c)     73 mm
d)    102 mm


34.                         According to Unwin's formula, the diameter of the rivet hole (in mm) can be obtained by:                   (t = thickness of the plate in mm)

                                                                                                         



35.                         Wahl correction factor takes care of:
a)     curvature effect
b)    shear stress correction
c)     both curvature effect and shear stress correction


36.                         In spring design, Wahl correction factor
a)     takes care of the direct shear stress in springs
b)    takes care of the curvature effect in springs
c)     takes care of the direct stress together with the curvature effect in springs


37.                         In a close coiled helical spring, the spring index (C) is given by D/d where D and d are the mean coil diameter and wire diameter respectively. For considering the effect of curvature, the Wahl’s stress factor K is given by
                                                                                       



38.                         Which of the following threads is used for transmission of power only in one direction?
a)     Acme thread
b)    Knuckle thread
c)     Buttress thread
d)    Square thread


39.                         V-threads are normally used for
a)     power transmission
b)    for securing two components
c)     not normally used


40.                         A bolt of M 24 × 2 means that
a)     the pitch of the thread is 24 mm and depth is 2 mm
b)    the cross-sectional area of the threads is 24 mm2 and number of starts is 2
c)     the nominal diameter of bolt is 24 mm and the pitch is 2 mm
d)    the effective diameter of the bolt is 24 mm and there are two threads per cm


41.                         The shear stress developed in the centre bolt (no-2) is

a)     35.3 MPa
b)    43.6 MPa
c)     6.4 MPa


42.                         For zero collar friction, the efficiency of a square-thread screw is:
(λ is lead angle and f is coefficient of friction of the screw)
                                                                                     



43.                         A single square thread power screw is to raise a load of 50 kN. A screw thread of major diameter of 34 mm and a pitch of 6 mm is used. The coefficient of friction at the thread and collar are 0.15 and 0.1 respectively. If the collar frictional diameter is 100 mm and the screw turns at a speed of 1 rev per second. The power input to the screw is
a)     1549 watts
b)    2300 watts
c)     2614 watts
d)    3167 watts


44.                         In the above question, the combined efficiency of the screw and collar is
a)     11.5%
b)    22.3%
c)     33.5%
d)    44.3%


45.                         The machine shown in the figure can be used for a tension test but not for a compression test. Should both screws have the same hand?

a)     Yes
b)    No, screws should always have different hands
c)     No, screws can have either same or different hands


46.                         In the machine shown below, both the screws have the same hand

a)     the machine can be used for a compression test only
b)    the machine can be used for a tension test only
c)     the machine can be used for both tension and compression tests


47.                         The purpose of Rebound clips in Laminated semi-elliptic spring is:
a)     to share the load from the master leaf to the graduated leaf
b)    to hold the leaves of the spring
c)     to prevent the deflected spring from touching the attached machine member
d)    to attach the spring with another machine member



48.                         The purpose of central clamp in Laminated semi-elliptic spring is:
a)     to share the load from the master leaf to the graduated leaf
b)    to hold the leaves of the spring
c)     to prevent the deflected spring from touching the attached machine member
d)    to attach the spring with another machine member


49.                         The purpose of camber in Laminated semi-elliptic spring is:
a)     to share the load from the master leaf to the graduated leaf
b)    to hold the leaves of the spring
c)     to prevent the deflected spring from touching the attached machine member
d)    to attach the spring with another machine member


50.                         Which of the following methods reduces additional stresses in laminated spring hinged at supports?
a)     Master leaf is made of stronger material than the other leaves
b)    Master leaf is made thinner than the other leaves
c)     Increase the radius of curvature of the master leaf than the next leaf
d)    All the above


51.                         Nipping of leaf spring
a)     Increases the stress in master leaf
b)    Decreases the stress in master leaf
c)     Doesn’t affect the stress in master leaf


52.                         A helical spring of wire diameter 6mm and spring index 6 is acted by an initial load of 800N. After compressing it further by 10mm the stress in the wire is 500MPa. Taking G = 84000MPa the number of active coils is
a)     13 turns
b)    21 turns
c)     27 turns
d)    32 turns


53.                         For a simple cantilever type leaf spring with uniform strength the leaf thickness can be given by
a)     σmax L3/2/(E δmax1/2)
b)    σmax L3/(E δmax2)
c)     σmax L2/(E δmax)
d)    σmax L4/(E δmax3)
Where δmax is the spring deflection, L is the characteristic length, σmax is the design stress or maximum stress and E is the Modulus of elasticity



54.                         Thermoplastic materials are those materials which
a)     are formed into shape under heat and pressure and results in a permanently hard product
b)    do not become hard with the application of heat and pressure and no chemical change occurs
c)     are flexible and can withstand considerable wear under suitable conditions
d)    are used as a friction lining for clutches and brakes


55.                         A cotter joint is used to transmit
a)     axial tensile load only
b)    axial compressive load only
c)     combined axial and twisting loads
d)    axial tensile or compressive loads


56.                         To ensure self-locking in a screw jack, it is essential that the helix angle is
a)     larger than friction angle
b)    smaller than friction angle
c)     equal to friction angle
d)    such as to give maximum efficiency in lifting


57.                         The figure shows a clamp coupling. If the effective number of bolts in each shaft is n/2, the allowable tensile stress for the bolt material is σt and the root diameter of the bolt is dc, then the clamping pressure between the shaft and the sleeve is

a)     nπdc2σt/(dL)
b)    nπdc2σt/(4dL)
c)     3nπdc2σt/(4dL)



58.                         In a typical clamp coupling the clamping pressure between the shaft and the sleeve is given by
a)     nπdc2σt/(dL)
b)    0.5nπdc3/2σt/(dL1/2)
c)     0.75nπdc4σt/(dL)2
d)    0.25nπdc2σt/(dL)
Where dc is the core diameter of the bolts, d is the clamp diameter, L the clamp length and σt is the tensile yield stress.




59.                         In a disc clutch, maximum pressure occurs
a)     at the inner radius
b)    at the centre
c)     at the outer radius


60.                         In which of the following, uniform pressure theory is more approximate?
a)     a new clutch
b)    an old clutch
c)     friction clutch


61.                         For a self-locking brake
a)     A large actuating force is needed
b)    A small actuating force is needed
c)     No actuating force is needed



62.                         If in the band brake shown below, drum diameter = 400mm, lining width = 75mm, rotational speed is 200 rpm, a = 250mm, m = 75mm, α = 2700, μ = 0.2 and the maximum lining pressure is 0.5 MPa, the torque is

a)     632 Nm
b)    915 Nm
c)     1150 Nm
d)    3160 Nm


63.                         Hydrodynamic Lubrication occurs at:
a)     Very low Sommerfeld Number
b)    Low Sommerfeld Number
c)     Medium Sommerfeld Number
d)    High Sommerfeld Number


64.                         Hydrodynamic Lubrication occurs at:
a)     At zero Sommerfeld number
b)    At relatively low Sommerfeld number
c)     At relatively high Sommerfeld number


65.                         Hydrodynamic lubricated bearings are
a)     Thick film bearings
b)    Thin film bearings
c)     Zero film bearings


66.                         When a shaft rotates in anticlockwise direction at slow speed in a bearing, then it will
a)     have contact at the lowest point of bearing
b)    move towards right of the bearing making metal to metal contact
c)     move towards left of the bearing making metal to metal contact
d)    move towards right of the bearing making no metal to metal contact



67.                         If Z = Absolute viscosity of the lubricant in kg/m-s, N = Speed of the journal in rpm, and p = Bearing pressure in N/mm2, then the bearing characteristic number is
a)     ZN/p
b)    Zp/N
c)     Z/Pn
d)    pN/Z



68.                         A ball bearing subjected to a radial load of 5 kN is expected to have a life of 8000 hours at 1450 rpm with a reliability of 99%. The dynamic load capacity of the bearing so that it can be selected from the manufacturer's catalogue based on a reliability of 90% is
a)     86.5 kN
b)    68.5 kN
c)     58.6 kN
d)    1 kN



69.                         The ball bearings are usually made from
a)     low carbon steel
b)    medium carbon steel
c)     high speed steel
d)    chrome nickel steel



70.                         The tapered roller bearings can take
a)     radial load only
b)    axial load only
c)     both radial and axial loads



71.                         The listed life of a rolling bearing, in a catalogue, is the
a)     minimum expected life
b)    maximum expected life
c)     average life



72.                         Which of the following are called as Anti-friction bearings?
a)     Fluid Film bearings
b)    Rolling contact bearings
c)     Sliding contact bearings
d)    Journal bearings



73.                         The load rating of a bearing is given for
a)     Axial loads only
b)    Radial loads only
c)     Both axial and radial loads



74.                         If two groups of identical ball bearings are tested under loads P1 and P2 for respective lives of L1 and L2 , then L1/L2 is
a)     (P1/P2)1/3
b)    (P2/P1)1/3
c)     (P1/P2)3
d)    (P2/P1)3


75.                         Which of the following is best suitable for high speeds of shaft and high loads?
a)     Journal bearing
b)    Ball bearing
c)     Roller bearing



76.                         Can a block moving over a constant height fluid film carry load?
a)     Yes
b)    No
c)     Depends upon viscosity of the fluid


77.                         If Sommerfeld number increases, then the Eccentricity ratio
a)     Increases
b)    Decreases
c)     Remains same



78.                         If Sommerfeld number increases, then the minimum film thickness
a)     Increases
b)    Decreases
c)     Remains same



79.                         If Sommerfeld number increases, then the ratio of side flow to total flow
a)     Decreases
b)    Increases
c)     Remains same



80.                         If Sommerfeld number increases, then the coefficient of friction
a)     Decreases
b)    Increases

c)     Remains same


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