1000+ Machine Design Multiple Choice Question Answer [Solved]

1. When spring index increases, the value of Wahl's stress factor
A. Increases linearly
B. Decreases linearly
C. Remains same
D. Increases exponentially
Answer : D

2. Tensile strength of a mild steel specimen can be roughly predicted from following hardness test
A. Brinell
B. Rockwell
C. Vickers
D. None of the above
Answer : A

3. Which is correct statement?
A. A member made of steel will generally be more rigid than a member of equal load carrying ability made of cast iron
B. A member made of cast iron will generally be more rigid than a member of equal load carrying ability made of steel
C. Both will be equally rigid
D. Which one is rigid will depend on several other factors
Answer : B

4. In helical gears, the right hand helixes on one gear will mesh __________ helixes on the other gear.
A. Right hand
B. Left hand
C. Both A and B
D. None of these
Answer : B

5. Coaxing is the procedure of increasing
A. Metal strength by cycling
B. Metal hardness by surface treatment
C. Metal resistance to corrosion by coating
D. Fatigue limit by overstressing the metal by successively increasing loadings
Answer : D

6. An elastic bar is fixed at the upper end and loaded at the lower end by a falling weight. The shock load produced can be reduced by
A. Increasing the length of bar
B. Decreasing the cross-sectional area of the bar
C. Decreasing the modulus of elasticity of the bar
D. All of the above
Answer : D

7. 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

8. 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

9. The helix angle for single helical gears ranges from
A. 10° to 15°
B. 15° to 20°
C. 20° to 35°
D. 35° to 50°
Answer : C

10. The condition for maximum power transmission is that the maximum tension in the flat belt should be equal to
A. 3 Pc
B. Pc
C. Pc/3
D. 2 Pc Where, Pc = tension in belt due to centrifugal force
Answer : A

11. A circular shaft can transmit a torque of 5 kN-m. If the torque is reduced to 4 kN-m, then the maximum value of bending moment that can be applied to the shaft is
A. 1 kN-m
B. 2 kN-m
C. 3 kN-m
D. 4 kN-m
Answer : C

12. 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

13. A bolt of uniform strength can be developed by
A. Keeping the core diameter of threads equal to the diameter of unthreaded portion of the bolt
B. Keeping the core diameter smaller than the diameter of the unthreaded portion
C. Keeping the nominal diameter of threads equal to the diameter of unthreaded portion of the bolt
D. None of the above
Answer : A

14. The coefficient of friction between the belt and pulley depends upon the
A. Material of belt and pulley
B. Slip of belt
C. Speed of belt
D. All of these
Answer : D

15. If d is the normal diameter of a bolt in mm, then the initial tension in kg in a bolt used for making a fluid tight joint as for steam engine cover joint is calculated by the relation
A. 124 d
B. 138 d
C. 151 d
D. 168 d
Answer : D

16. In the case of an elastic bar fixed at upper end and loaded by a falling weight at lower end, the shock load produced can be decreased by
A. Decreasing the cross-section area of bar
B. Increasing the cross-section area of bar
C. Remain unaffected with cross-section area
D. Would depend upon other factors
Answer : A

17. The backlash for spur gears depends upon
A. Module
B. Tooth profile
C. Both module and pitch line velocity
D. Pitch line velocity
Answer : C

18. The bending moment M and a torque T is applied on a solid circular shaft. If the maximum bending stress equals to maximum shear stress developed, then M is equal to
A. T/2
B. T
C. 2T
D. 4T
Answer : A

19. Spring index is
A. Ratio of coil diameter to wire diameter
B. Load required to produce unit deflection
C. Its capability of storing energy
D. Indication of quality of spring
Answer : A

20. Plastic flow in ductile materials
A. Increases the seriousness of static loading stress concentration
B. Lessens the seriousness of static loading stress concentration
C. Has no effect on it
D. Depends on other considerations
Answer : B

21. According to Indian standards, total numbers of fundamental deviations are
A. 10
B. 15
C. 20
D. 25
Answer : D

22. A tap bolt
A. Has a head on one end and a nut fitted to the other
B. Has head at one end and other end fits into a tapped hole in the other part to be joined
C. Has both the ends threaded
D. Has pointed threads
Answer : B

23. The ratio of endurance limit in shear to the endurance limit in flexure is
A. 0.33
B. 0.4
C. 0.5
D. 0.55
Answer : D

24. Crushing resistance required to crush the rivet per pitch length is
A. p.d.?_c
B. p.t.?_c
C. n.d.t.?_c
D. (p - d) t.?_c
Answer : C

25. A feather key is generally
A. Loose in shaft and tight in hub
B. Tight in shaft and loose in hub
C. Tight in both shaft and hub
D. Loose in both shaft and hub
Answer : B

26. In standard taper roller bearings, the angle of taper of outer raceway is
A. 5°
B. 8°
C. 15°
D. 25°
Answer : D

27. Deep groove ball bearings are used for
A. Heavy thrust load only
B. Small angular displacement of shafts
C. Radial load at high speed
D. Combined thrust and radial loads at high speed
Answer : D

28. The draw of cotter need not exceed
A. 3 mm
B. 5 mm
C. 10 mm
D. 20 mm
Answer : A

29. The value of Lewis form factor used in design of gears is
A. Dependent on number of teeth of a gear
B. Dependent on system of teeth
C. Independent of size of teeth
D. All of these
Answer : D

30. During hot working of metals,
A. Porosity of the metal is largely eliminated
B. Grain structure of the metal is refined
C. Mechanical properties are improved due of refinement of grains
D. All of the above
Answer : D

31. A double fillet welded joint with parallel fillet weld of length l and leg s is subjected to a tensile force P. Assuming uniform stress distribution, the shear stress in the weld is given by
A. ?2P/s.l
B. P/2.s.l
C. P/?2.s.l
D. 2P/s.l
Answer : C

32. A screw is said to be over hauling screw, if the
A. Friction angle is less than helix angle
B. Friction angle is more than helix angle
C. Friction angle is equal to helix angle
D. Efficiency of screw is 100%
Answer : A

33. The cracks in helical springs used in railway carriages usually start on the inner side of the coil because of the fact that
A. It is subjected to a higher cyclic loading than the outer side
B. It is subjected to a higher stress than the outer side
C. It is more stretched than the outer side during the manufacturing process
D. It has a lower curvature than the outer side
Answer : A

34. 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

35. The pitch of threads on a Jock nut in comparison to pitch of nut is
A. Same
B. Coarser
C. Finer
D. Very fine
Answer : A

36. Which of the following statement is correct, for two shafts connected in parallel?
A. Torque in each shaft is the same
B. Shear stress in each shaft is the same
C. Angle of twist of each shaft is the same
D. Torsional stiffness of each shaft is the same
Answer : C

37. When the screw in a mechanical screw jack rotates, the load kept on the top of it moves
A. Axially upwards
B. Axially downwards
C. Axially upwards or downwards
D. None of these
Answer : C

38. Which of the following pipe joints would be suitable for pipes carrying steam?
A. Flanged
B. Threaded
C. Bell and spigot
D. Expansion
Answer : D

39. Which is correct statement? Stress concentration in static loading is
A. Very serious in brittle materials and less serious in ductile materials
B. Very serious in ductile materials and less serious in brittle materials
C. Equally serious in both types of materials
D. Seriousness would depend on other factors
Answer : A

40. A hollow saddle key is
A. A taper key which fits half in the key way of hub and half in the key way of shaft
B. A taper key which fits in a key way of the hub and is flat on the shaft
C. A taper key which fits in a key way of the hub and the bottom of the key is shaped to fit the curved surface of the shaft
D. Provided in pairs at right angles and each key is to withstand torsion in one direction only
Answer : C

41. Rivets are generally specified by
A. Thickness of plates to be riveted
B. Length of rivet
C. Diameter of head
D. Nominal diameter
Answer : D

43. The endurance limit of a material with finished surface in comparison to rough surface is
A. More
B. Less
C. Same
D. More or less depending on quantum of load
Answer : A

44. The resultant axial load on a bolt depends on
A. Initial tension
B. External load applied
C. Relative elastic yielding (springness) of the bolt and the connected member
D. All of the above
Answer : D

45. Pick up wrong statement. Fatigue strength can be increased by
A. Cold working
B. Shot peening
C. Grinding and lapping surface
D. Hot working
Answer : D

46. A compound cylinder with inner radius 50 mm and outer radius 70 mm is made by shrinking one cylinder on to the other cylinder, the junction radius is 60 mm and the junction pressure is 1.1 N/mm². The maximum hoop stress developed in the inner cylinder is
A. 3.6 N/mm² compression
B. 3.6 N/mm² tension
C. 7.2 N/mm² compression
D. 7.2 N/mm² tension
Answer : C

47. The shear stress in a beam varies from zero at the outer fibres to a maximum at the________.
A. Neutral surface
B. Upper surface
C. Lower surface
D. None of these
Answer : A

48. The notch sensitivity q is expressed in terms of fatigue stress concentration factor Kf and theoretical stress concentration factor Kt as
A. (K_f + 1)/ (K_t + 1)
B. (K_f - 1)/ (K_t - 1)
C. (K_t + 1)/ (K_f + 1)
D. (K_t - 1)/ (K_f - 1)
Answer : B

49. In designing a sleeve coupling, length of the sleeve is taken as (where d = Diameter of the shaft)
A. d + 17 mm
B. 2d + 13 mm
C. 2d + 20 mm
D. 3.5d
Answer : D

50. 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