1000+ Machine Design MCQ for NMAT [Solved]

1. Which of the following is not correct procedure to increase the fatigue limit?
A. Cold working
B. Shot peening
C. Surface decarburisation
D. Under stressing
Answer : C

2. When compared to the rod of the same diameter and material, a wire rope
A. Is less flexible
B. Has a much smaller load carrying capacity
C. Does not provide much warning before failure
D. Provides much greater time for remedial action before failure
Answer : B

3. Resistance to fatigue of a material is measured by
A. Young's modulus
B. Coefficient of elasticity
C. Elastic limit
D. Endurance limit
Answer : D

4. 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

5. The most important dimension in the design of a nut is
A. Pitch diameter
B. Inside diameter
C. Outside diameter
D. Height
Answer : D

6. 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

7. When a helical compression spring is cut into halves, the stiffness of the resulting spring will be
A. Same
B. Double
C. One-half
D. One-fourth
Answer : B

8. A shaft is subjected to a maximum bending stress of 80 N/mm² and maximum shearing stress equal to 30 N/mm² at a particular section. If the yield point in tension of the material is 280 N/mm² and the maximum shear stress theory of failure is used, then the factor of safety obtained will be
A. 2.5
B. 2.8
C. 3.0
D. 3.5
Answer : B

9. 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

10. The maximum normal stress theory is used for
A. Plastic materials
B. Brittle materials
C. Non-ferrous materials
D. Ductile materials
Answer : B

11. The centre distance between two meshing involute gears is equal to
A. (Sum of base circle radii)/cos?
B. (Difference of base circle radii)/cos?
C. (Sum of pitch circle radii)/cos?
D. (Difference of pitch circle radii)/cos?
Answer : A

12. For a shaft diameter of 100 mm, the number of bolts in a flange coupling should be
A. 4
B. 6
C. 8
D. 10
Answer : A

13. A shaft is subjected to fluctuating loads for which the normal torque (T) and bending moment (M) are 1000 N-m and 500 N-m respectively. If the combined shock and fatigue factor for bending is 1.5 and combined shock and fatigue factor for torsion is 2, then the equivalent twisting moment for the shaft is
A. 2000 N-m
B. 2050 N-m
C. 2100 N-m
D. 2136 N-m
Answer : D

14. Eulers formula for a mild steel column is not valid if the slenderness ratio is
A. 90
B. 60
C. 120
D. 100
Answer : B

15. 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

16. In a multiple V-belt drive, when a single belt is damaged, it is preferable to change the complete set in order to
A. Reduce vibration
B. Reduce slip
C. Ensure uniform loading
D. Ensure proper alignment
Answer : C

17. The resilience of a bolt may be increased by
A. Increasing its shank diameter
B. Increasing its length
C. Decreasing its shank diameter
D. Decreasing its length
Answer : B

18. In order to determine the stresses in a thin cylinder due to an internal pressure, it is assumed that
A. The effect of curvature of the cylinder wall is neglected
B. The tensile stresses are uniformly distributed over the section of the walls
C. The effect of the restraining action of the heads at the end of the pressure vessel is neglected
D. All of the above
Answer : D

19. The maximum bending stress in a curved beam having symmetrical section always occur at the
A. Centroidal axis
B. Neutral axis
C. Inside fibre
D. Outside fibre
Answer : C

20. Stress concentration in static loading is more serious in
A. Ductile materials
B. Brittle materials
C. Equally serious in both cases
D. Depends on other factors
Answer : B

22. Which process will increase the fatigue duration of parts?
A. Finishing and polishing
B. Shotpeening
C. De-carburisation
D. Electroplating
Answer : B

23. A column is known as a long column if the slenderness ratio is
A. 40
B. 50
C. 70
D. 100
Answer : D

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

25. For longitudinal joint in boilers, the type of joint used is
A. Butt joint with single cover plate
B. Butt joint with double cover plate
C. Lap joint with one ring overlapping the other
D. Any one of the above
Answer : B

26. In designing a flange coupling, the pitch circle diameter of bolts is taken as (where d = Diameter of the shaft)
A. 2d
B. 3d
C. 4d
D. 5d
Answer : B

27. When a close coiled helical spring is compressed, its wire is subjected to
A. Tension
B. Shear
C. Compression
D. All of the above
Answer : A

28. A sliding bearing which operates without any lubricant present, is called
A. Zero film bearing
B. Boundary lubricated bearing
C. Hydrodynamic lubricated bearing
D. Hydrostatic lubricated bearing
Answer : A

29. In a belt drive, if the pulley diameter is doubled keeping the tension and belt width constant, then it will be necessary to
A. Increase the key length
B. Increase the key depth
C. Increase the key width
D. Decrease the key length
Answer : A

30. The maximum stress due to stress concentration in a bar having circular transverse hole, as compared to its static stress without hole will be
A. Same in both cases
B. 2 times more
C. 3 times more
D. 4 times more
Answer : C

31. In a boundary lubricated bearing, there is a __________ of lubricant between the journal and the bearing.
A. Thick film
B. Thin film
C. Either A or B
D. None of these
Answer : B

32. The usual clearance provided in hydrodynamic bearing per mm of diameter of shaft is
A. 0.01 micron
B. 0.1 micron
C. 1 micron
D. 10 microns
Answer : C

33. In leaf springs, the longest leaf is known as
A. Master leaf
B. Lower leaf
C. Upper leaf
D. None of these
Answer : A

34. For maximum power, the velocity of the belt will be
A. ?(T/m)
B. ?(T/2m)
C. ?(T/3m)
D. None of these
Answer : C

35. If P1 and P2 are the tight and slack side tensions in the belt, then the initial tension Pi (neglecting centrifugal tension) will be equal to
A. P₁ - P₂
B. P₁ + P₂
C. ?2 × (P₁ + P₂)
D. [?2 × (P₁ + P₂)] + P_c Where Pc is centrifugal tension
Answer : C

36. Which of the following cotter joint will be used to connect strap end of a connecting rod?
A. Spigot and socket cotter joint
B. Sleeve and cotter joint
C. Gib and cotter joint
D. Any one of these
Answer : C

37. According to Indian standards, the diameter of rivet hole is made larger than the basic size of rivet by
A. 0.5 mm upto rivet diameter of 24 mm
B. 1 mm for rivet diameter from 27 mm to 36 mm
C. 2 mm for rivet diameter from 39 mm to 48 mm
D. All of the above
Answer : C

38. 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

39. If p = bearing pressure on projected bearing area, z = absolute viscosity of lubricant, and N = speed of journal, then the bearing characteristic number is given by
A. ZN/p
B. p/ZN
C. Z/pN
D. N/Zp
Answer : A

40. The spring mostly used in gramophones is
A. Helical spring
B. Conical spring
C. Flat spiral spring
D. Volute spring
Answer : C

41. 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

42. Which of the following screw thread is used for power transmission in one direction only?
A. Square threads
B. Multiple threads
C. Acme threads
D. Buttress threads
Answer :