Machine Design 1000+ MCQ with answer for RRB NTPC

1. A key made from a cylindrical disc having segmental cross-section, is known as
A. Woodruff key
B. Feather key
C. Flat saddle key
D. Gib head key
Answer : A

2. A connecting rod subjected to an axial load may buckle with
A. X-axis as neutral axis
B. Y-axis as neutral axis
C. X-axis or Y-axis as neutral axis
D. Z-axis
Answer : C

3. The smallest diameter of an external or internal screw thread is known as
A. Minor diameter
B. Major diameter
C. Pitch diameter
D. None of these
Answer : A

4. The acme threads are usually found on
A. Spindles of bench vices
B. Railway carriage couplings
C. Feed mechanism of machine tools
D. Screw cutting lathes
Answer : D

5. The design calculations for members subject to fluctuating loads with the same factor of safety, yield the most conservative estimates when using
A. Gerber relation
B. Soderberg relation
C. Goodman relation
D. None of these
Answer : C

6. A connecting rod should be
A. Strong in buckling about X-axis
B. Strong in buckling about Y-axis
C. Equally strong in buckling about X-axis and Y-axis
D. Any one of the above
Answer : C

7. Screws used for power transmission should have
A. Very fine threads
B. High efficiency
C. Low efficiency
D. Strong teeth
Answer : B

8. The permissible stress in the fillet weld is 100 N/mm². The fillet weld has equal leg lengths of 15 mm each. The allowable shearing load on the weldment per cm length of the weld is
A. 7.5 kN
B. 10.6 kN
C. 15 kN
D. 22.5 kN
Answer : B

9. In order to permit the thermal expansion/contraction of tubing, it should be
A. Crimped
B. Honed
C. Flared
D. Bent
Answer : D

10. The effective stress in wire ropes during normal working is equal to the stress due to
A. Axial load plus stress due to bending
B. Acceleration/retardation of masses plus stress due to bending
C. Axial load plus stress due to acceleration/retardation
D. Bending plus stress due to acceleration/retardation
Answer : A

11. Lewis form factor for 14 ½° composite and full depth involute system is (where T = Number of teeth)
A. 0.124 - (0.684/T)
B. 0.154 - (0.912/T)
C. 0.175 - (0.841/T)
D. None of these
Answer : A

12. When a hole of diameter d is punched in a metal of thickness 't', then the force required to punch a hole is equal to (where ?u = Ultimate shear strength of the material of the plate)
A. d.t.?_u
B. ?d.t.?_u
C. ?/4 × d².?_u
D. ?/4 × d² × t.?_u
Answer : B

13. In a flange coupling, the bolts are subjected to
A. Tensile stress
B. Compressive stress
C. Shear stress
D. None of these
Answer : C

14. The efficiency of a square threaded screw is maximum if the helix angle is equal to (Where ? = Angle of friction)
A. 90° - ?
B. 45° - ?
C. 45° - ?/2
D. 45° + ?/2
Answer : C

15. When a nut is tightened by placing a washer below it, the bolt will be subjected to following type of loads
A. Compression
B. Tension
C. Shear
D. Combined loads
Answer : B

16. The ultimate strength of steel in tension in comparison to shear is in the ratio of
A. 1 : 1
B. 2 : 1
C. 3 : 2
D. 2 : 3
Answer : C

17. In unilateral system of tolerance, the tolerance is allowed on
A. Both sides of the actual size
B. One side of the actual size
C. One side of the nominal size
D. Both sides of the nominal size
Answer : C

18. The stretching in a belt can be controlled by __________ the stress in the belt.
A. Reducing
B. Increasing
C. Both A and B
D. None of these
Answer : A

19. In a butt welded joint, the size of weld is __________ the throat of weld.
A. 0.5 times
B. Equal to
C. 2 times
D. Double
Answer : B

20. The helix angle for double helical gears may be made up to
A. 45°
B. 60°
C. 75°
D. 90°
Answer : A

21. An open coiled helical compression spring 'A' of mean diameter 50 mm is subjected to an axial load W. Another spring 'B' of mean diameter 25 mm is similar to spring 'A' in all respects. The deflection of spring 'B' will be __________ as compared to spring 'A'.
A. One-eighth
B. One-fourth
C. One-half
D. Double
Answer : A

22. The velocity factor for precision metallic gears cut with high accuracy and operating at velocities upto 20 m/s is equal to
strong>A. 0.75/ (0.75 + ?v)
B. 3/ (3 + v)
C. 4.5/ (4.5 + v)
D. 6/ (6 + v)
Answer : A

23. The tension on the slack side of the belt is __________ the tension on the tight side of the belt.
A. Equal to
B. Less than
C. Greater than
D. None of these
Answer : B

24. When the connected members are very yielding (soft gasket) as compared to the bolt, then the resultant load on the bolt will be equal to the
A. Initial tension
B. External load applied
C. Sum of the initial tension and external load applied
D. Initial tension or external load, whichever is greater
Answer : C

25. The maximum efficiency of a square threaded screw is
A. (1 - sin?)/ (1 + sin?)
B. (1 + sin?)/ (1 - sin?)
C. (1 - sin?)/ (1 + cos?)
D. (1 + cos?)/ (1 - sin?)
Answer : A

26. In the assembly of pulley, key and shaft
A. Pulley is made the weakest
B. Key is made the weakest
C. Key is made the strongest
D. All the three are designed for equal strength
Answer : B

27. When the connected members are very yielding (soft gasket) as compared to the bolt, then the resultant load on the bolt will be equal to the
A. Initial tension
B. External load applied
C. Sum of the initial tension and external load applied
D. Initial tension or external load, whichever is greater
Answer : C

28. For a shoe brake, the equivalent coefficient of friction is equal to (where ? = Actual coefficient of friction, and ? = Semi-block angle)
A. 2? sin?/(? + sin?)
B. ? sin?/(2? + sin 2?)
C. 4? sin?/(? + sin?)
D. 4? sin?/(2? + sin 2?)
Answer : D

29. A localised compressive stress at the area of contact between two members is known as
A. Tensile stress
B. Bending stress
C. Bearing stress
D. Shear stress
Answer : C

30. If a load W is applied instantaneously on a bar; Then the stress induced in bar will
A. Be independent of ratio of mass of load W to mass of bar (y)
B. Increase with increase in y
C. Decrease with decrease in y
D. Depend on other considerations
Answer : A

31. If a shaft made from ductile material is subjected to combined bending and twisting moment, calculations based on which one of the following failure theories will give the most conservative value?
A. Maximum principal stress theory
B. Maximum shear stress theory
C. Maximum strain energy theory
D. Maximum distortion energy theory
Answer : A

32. The shock resistance of steel is increased by adding
A. Nickel
B. Chromium
C. Nickel and chromium
D. Cobalt and molybdenum
Answer : C

33. According to I.B.R., the efficiency of a double riveted butt joint with double cover straps of equal width should be
A. 45 to 60 %
B. 63 to 70 %
C. 70 to 83 %
D. 80 to 90 %
Answer : C

34. Tapered roller bearings can take
A. Axial load only
B. Both radial and axial loads and the ratio of these being greater than unity
C. Radial load only
D. Both radial and axial loads and the ratio of these being less than unity
Answer : B

35. In a band and block brake, the ratio of tensions on the tight and slack sides of band is given by (where ? = Coefficient of friction between the blocks and the drum, ? = Semi-angle of each block subtending at the centre of drum, and n = Number of blocks)
A. T?/T? = ?? × n
B. T?/T? = (??)ⁿ
C. T?/T? = [(1 - ? tan?)/ (1 + ? tan?)]ⁿ
D. T?/T? = [(1 + ? tan?)/ (1 - ? tan?)]ⁿ
Answer : D

36. The ratio of the ultimate stress to the design stress is known as
A. Elastic limit
B. Strain
C. Factor of safety
D. Bulk modulus
Answer : C

37. If T is the actual number of teeth on a helical gear and ? is the helix angle for the teeth, then formative number of teeth is written as
A. T sec³?
B. T sec²?
C. T/sec³?
D. T cosec?
Answer : A

38. Which of the following statement is correct?
A. A parallel sunk key is a taperless key
B. A parallel sunk key may be rectangular or square in cross-section
C. A flat saddle key is a taper key which fits in a key way of the hub and is flat on the shaft
D. All of the above
Answer : D

39. The period during which the cam follower remains at rest, when cam moves, is known as
A. Constant period
B. Fixed period
C. Dwell period
D. Idle period
Answer : C

40. An open belt drive is used when
A. Shafts are arranged at right angles and rotate in one definite direction
B. Shafts are arranged parallel and rotate in the opposite directions
C. Shafts are arranged parallel and rotate in the same directions
D. Driven shaft is to be started or stopped whenever desired without interfering with the driving shaft
Answer : C

41. A special case of ductility which permits materials to be rolled or hammered into thin sheets, is called
A. Plasticity
B. Elasticity
C. Ductility
D. Malleability
Answer : D

42. The standard length of the shaft is
A. 6 m
B. 5 m
C. 7 m
D. All of these
Answer : D

43. The circumferential and longitudinal strains in a cylindrical boiler under internal steam pressure are ?c and ?l respectively. The change in volume of the boiler cylinder per unit volume will be
A. ?_c + 2?_l
B. 2?_c + ?_l
C. ?_c + ?_l²
D. ?_c² + ?_l
Answer : B

44. In worm, gears, pitch lead angle is
A. Half the angle between two inclined faces in axial plane
B. The angle between the tangent to the pitch helix and the plane of rotation
C. The angle between the tangent to the pitch helix and an element of the cylinder
D. None of the above
Answer : B

45. Which of the following coupling is used to connect two shafts which have both lateral and angular misalignment?
A. Bushed pin type coupling
B. Universal coupling
C. Oldham coupling
D. All of these
Answer : D

46. The fatigue stress concentration factor is defined as
A. The ratio of endurance limit with stress concentration to the endurance limit without stress concentration
B. The ratio of endurance limit without stress concentration to the endurance limit with stress concentration
C. The product of the endurance limits with and without stress concentration
D. All of the above
Answer : B

47. If the centre distance of the mating gears having involute teeth is varied within limits, the velocity ratio.
A. Increases
B. Decreases
C. Remains unchanged
D. None of these
Answer : C

48. In designing a connecting rod, it is considered like __________ for buckling about X-axis.
A. Both ends hinged
B. Both ends fixed
C. One end fixed and the other end hinged
D. One end fixed and the other end free
Answer : A

49. In a marine flange coupling, the thickness of flange is taken as
A. d/2
B. d/3
C. 3d/4
D. d/4
Answer : B

50. The shear plane in case of bolts should
A. Be across threaded portion of shank
B. Be parallel to axis of bolt
C. Be normal to threaded portion of shank
D. Never be across the threaded portion
Answer : D