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NHPC Paper - Mechanical Engineering
1.In abrasive jet machining, as the distance between the nozzle tip and the work surface increases, the material removal rate
(A) increases continuously.
(B) decreases continuously.
(C) decreases, becomes stable and then increases.
(D) increases, becomes stable and then decreases.
2. During normalizing process of steel,the specimen is heated
(A) between the upper and lower critical temperature and cooled in still air.
(B) above the upper critical temperature and cooled in furnace.
(C) above the upper critical temperature and cooled in still air.
(D) between the upper and lower critical temperature and cooled in furnace.
3. The following are the data for two crossed helical gears used for speed reduction:Gear I : Pitch circle diameter in the plane of rotation 80 mm and helix angle 30º Gear II : Pitch circle diameter in the plane of rotation 120 m and helix angle 22.5º If the input speed is 1440 rpm, the output speed in rpm is
(A) 1200
(B) 900
(C) 875
(D) 720
4. A thin walled spherical shell is subjected to an internal pressure. If the radius of the shell is increased by 1% and the thickness is reduced by 1%, with the internal pressure remaining the same, the percentage change in the circumferential (hoop) stress is
(A) 0
(B) 1
(C) 1.08
(D) 2.02
5. Which one of the following is NOT a decision taken during the aggregate production planning stage?
(A) Scheduling of machines
(B) Amount of labour to be committed
(C) Rate at which production should happen
(D) Inventory to be carried forward
6. A CNC vertical milling machine has to cut a straight slot of 10 mm width and 2 mm depth by a cutter of 10 mm diameter between points (0, 0) and (100, 100) on the XY plane (dimensions in mm). The feed rate used for milling is 50 mm/min. Milling time for the slot (in seconds) is
(A) 120
(B) 170
(C) 180
(D) 240
7. A solid cylinder of diameter 100 mm and height 50 mm is forged between two frictionless flat dies to a height of 25 mm. The percentage change in diameter is
(A) 0
(B) 2.07
(C) 20.7
(D) 41.4
8. Which one of the following configurations has the highest fin effectiveness?
(A) Thin, closely spaced fins
(B) Thin, widely spaced fins
(C) Thick, widely spaced fins
(D) Thick, closely spaced fins
9. A circular solid disc of uniform thickness 20 mm, radius 200 mm and mass 20 kg, is used as a flywheel. If it rotates at 600 rpm, the kinetic energy of the flywheel, in Joules is
(A) 395
(B) 790
(C) 1580
(D) 3160
10. For a long slender column of uniform cross section, the ratio of critical buckling load for the case with both ends clamped to the case with both ends hinged is
(A) 1
(B) 2
(C) 4
(D) 8
11. In a single pass drilling operation, a through hole of 15 mm diameter is to be drilled in a steel plate of 50 mm thickness.Drill spindle speed is 500 rpm, feed is 0.2 mm/revand drill point angle is 118°. Assuming 2 mm clearance at approach and exit, the total drill time (in seconds) is
(A) 35.1
(B) 32.4
(C) 31.2
(D) 30.1
12. An incompressible fluid flows over a flat plate with zero pressure gradient. The boundary layer thickness is 1 mm at a location where the Reynolds number is 1000. If the velocity of the fluid alone is increased by a factor of 4, then the boundary layer thickness at the same location, in mmwill be
(A) 4
(B) 2
(C) 0.5
(D) 0.25
13. A room contains 35 kg of dry air and 0.5 kg of water vapor. The total pressure and temperature of air in the room are 100 kPa and 25°C respectively. Given that the saturation pressure for water at 25°C is 3.17 kPa, the relative humidity of the air in the room is
(A) 67%
(B) 55%
(C) 83%
(D) 71%
14. In a single pass rolling process using 410 mm diameter steel rollers, a strip of width 140 mm and thickness 8 mm undergoes 10 % reduction of thickness. The angle of bite in radians is
(A) 0.006
(B) 0.031
(C) 0.062
(D) 0.600
15. Water (Cp= 4.18 kJ/kg.K) at 80°C enters a counterflow heat exchanger with a mass flow rate of 0.5 kg/s. Air (Cp= 1 kJ/kg.K) enters at 30°Cwith a mass flow rate of 2.09 kg/s. If the effectiveness of the heat exchanger is 0.8, the LMTD (in °C) is
(A) 40
(B) 20
(C) 10
(D) 5
16. A solid circular shaft needs to be designed to transmit a torque of 50 N.m. If the allowable shear stress of the material is 140 MPa, assuming a factor of safety of 2, the minimum allowable design diameter in mm is
(A) 8
(B) 16
(C) 24
(D) 32
17. A box contains 4 red balls and 6 black balls. Three balls are selected randomly from the box one after another, without replacement. The probability that the selected set contains one red ball and two black balls is
(A) 1/20
(B) 1/12
(C) 3/10
(D) 1/2
18. Choose the most appropriate alternative from the options given below to complete the following sentence:
Sureshs dog is the one was hurt in the stampede.
(A) that
(B) which
(C) who
(D) whom
19. Choose the most appropriate alternative from the options given below to complete the following sentence:
Despite several the mission succeeded in its attempt to resolve the conflict.
(A) attempts
(B) setbacks
(C) meetings
(D) delegations
20. Which one of the following options is the closest in meaning to the word given below?
Mitigate
(A) Diminish
(B) Divulge
(C) Dedicate
(D) Denote
21. Choose the grammatically INCORRECT sentence:
(A) They gave us the money back less the service charges of Three Hundred rupees.
(B) This countrys expenditure is not less than that of Bangladesh.
(C) The committee initially asked for a funding of Fifty Lakh rupees, but later settled for a lesser sum.
(D) This countrys expenditure on educational reforms is very less.
22. Given the sequence of terms, AD, CG, FK, JP, the next term is
(A) OV
(B) OW
(C) PV
(D) PW
23. Wanted Temporary, Part-time persons for the post of Field Interviewer to conduct personal interviews to collect and collate economic data. Requirements: High School-pass, must be available for Day, Evening and Saturday work. Transportation paid, expenses reimbursed. Which one of the following is the best inference from the above advertisement?
(A) Gender-discriminatory
(B) Xenophobic
(C) Not designed to make the post attractive
(D) Not gender-discriminatory
24. An automobile plant contracted to buy shock absorbers from two suppliers X and Y. X supplies 60% and Y supplies 40% of the shock absorbers. All shock absorbers are subjected to a quality test. The ones that pass the quality test are considered reliable. Of Xs shock absorbers, 96% are reliable. Of Ys shock absorbers, 72% are reliable. The probability that a randomly chosen shock absorber, which is found to be reliable, is made by Y is
(A) 0.288
(B) 0.334
(C) 0.667
(D) 0.720
25. Which of the following assertions are CORRECT?
P: Adding 7 to each entry in a list adds 7 to the mean of the list
Q: Adding 7 to each entry in a list adds 7 to the standard deviation of the list
R: Doubling each entry in a list doubles the mean of the list
S: Doubling each entry in a list leaves the standard deviation of the list unchanged
(A) P, Q
(B) Q, R
(C) P, R
(D) R, S
