1000+ Machine Design MCQ for UPSC CDS [Solved]

1. An imaginary circle which by pure rolling action gives the same motion as the actual gear, is called
A. Addendum circle
B. Dedendum circle
C. Pitch circle
D. Clearance circle
Answer : C

2. Which of the following screw thread is adopted for power transmission in either direction?
A. Acme threads
B. Square threads
C. Buttress threads
D. Multiple threads
Answer : B

3. In a horizontal flat belt drive, it is customary to use
A. Bottom side of belt as slack side
B. Top side of belt as slack side
C. Idler pulley
D. None of the above
Answer : B

4. Rankine's theory is used for
A. Brittle materials
B. Ductile materials
C. Elastic materials
D. Plastic materials
Answer : A

5. Two shafts A and B are made of the same material. The diameter of shaft A is twice as that of shaft B. The power transmitted by the shaft A will be __________ of shaft B.
A. Twice
B. Four times
C. Eight times
D. Sixteen times
Answer : C

6. Resilience of a material is important, when it is subjected to
A. Combined loading
B. Fatigue
C. Thermal stresses
D. Shock loading
Answer : D

7. 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

8. 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

9. A self locking screw has
A. Fine threads
B. Course threads
C. Coefficient of friction is greater than tangent of load angle
D. Hole for inserting split pin
Answer : C

10. 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

11. When the fulcrum is in between the load and effort, the lever is said to be of
A. First type
B. Second type
C. Third type
D. Any one of these
Answer : A

12. 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

13. A spring is used to
A. Measure forces
B. Apply forces
C. Store energy
D. All of these
Answer : D

14. The contact ratio is the ratio of
A. Length of arc of recess to the circular pitch
B. Length of path of contact to the circular pitch
C. Length of arc of contact to the circular pitch
D. Length of arc of approach to the circular pitch
Answer : C

15. The objective of idler pulley in belt drive is to
A. Decrease the tendency of belt to slip
B. Increase the power transmission capacity
C. Increase the wrap angle and belt tension
D. All the above objectives
Answer : D

16. The elasticity is the property of a material which enables it to
A. Regains its original shape after deformation when the external forces are removed
B. Draw into wires by the application of a tensile force
C. Resists fracture due to high impact loads
D. Retain deformation produced under load permanently
Answer : A

17. 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

18. 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

19. Which of the following statement is wrong?
A. A key is used as a temporary fastening
B. A key is subjected to tensile stresses
C. A key is always inserted parallel to the axis of the shaft
D. A key prevents relative motion between the shaft and boss of the pulley
Answer : B

20. The largest 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 : B

21. If the centre distance of the mating gears having involute teeth is increased, then the pressure angle
A. Increases
B. Decreases
C. Remains unchanged
D. None of these
Answer : A

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

23. 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

24. A coupling used to connect two perfectly aligned shafts, is
A. Muff coupling
B. Compression coupling
C. Flange coupling
D. All of these
Answer : D

25. Two shafts of the same length and material are joined in series. If the ratio of their diameters is 2, then the ratio of their angles of twist will be
A. 2
B. 4
C. 8
D. 16
Answer : D

26. 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

27. A universal coupling is used to connect two shafts
A. Which are not in exact alignment
B. Which are perfectly aligned
C. Whose axes intersect at a small angle
D. Have lateral misalignment
Answer : C

28. 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

29. I.S. specifies following total number of grades of tolerances
A. 18
B. 16
C. 20
D. 22
Answer : A

30. Endurance limit or fatigue limit is the maximum stress that a member can withstand for an infinite number of load applications without failure when subjected to
A. Dynamic loading
B. Static loading
C. Combined static and dynamic loading
D. Completely reversed loading
Answer : D

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

32. For general industrial machinery, the ratio of the length of journal to its diameter is taken as
A. 0.5 to 1
B. 1 to 2
C. 3 to 5
D. 5 to 10
Answer : B

33. A locking device extensively used in marine type connecting rod ends is a
A. Jam nut
B. Castle nut
C. Sawn nut
D. Ring nut
Answer : D

34. In case of V-belt drive
A. The belt should touch the bottom of groove in the pulley
B. The belt should not touch the bottom of groove in the pulley
C. The belt should not touch the sides of groove in the pulley
D. None of the above
Answer : B

35. According to Rankine's theory, the failure occurs at a point in a member
A. When the maximum shear stress in a biaxial stress system reaches the shear stress at elastic limit in a simple tension test
B. When the maximum principal stress in a biaxial stress system reaches the elastic limit of the material in a simple tension test
C. When the strain energy per unit volume in a biaxial stress system reaches the strain energy at the elastic limit per unit volume as determined from a simple tension test
D. When the maximum principal strain in a biaxial stress system reaches the strain at the elastic limit as determined from a simple tension test
Answer : B

36. For circumferential 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 : C

37. 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

38. In the calculation of induced shear stress in helical springs, the Wahl's stress factor is used to take care of
A. Combined effect of transverse shear stress and bending stress in the wire
B. Combined effect of bending stress and curvature of the wire
C. Combined effect of transverse shear stress and curvature of wire
D. Combined effect of torsional shear stress and transverse shear stress in the wire
Answer : B

39. In hydrodynamic bearings
A. The oil film pressure is generated only by the rotation of the journal
B. The oil film is maintained by supplying oil under pressure
C. Do not require external supply of lubricant
D. Grease is used for lubrication
Answer : A

40. The size of a cam depends upon
A. Base circle
B. Pitch circle
C. Prime circle
D. Pitch curve
Answer : A

41. The lower deviation is the algebrai difference between the
A. Actual size and the corresponding basic size
B. Maximum limit and the basic size
C. Minimum limit and the basic size
D. None of the above
Answer : C

42. In a flat belt drive, if the slip between the driver and belt is 1 %, between the belt and follower is 3% and driver and follower pulley diameters are equal, then velocity ratio of the drive will be
A. 0.96
B. 0.97
C. 0.98
D. 0.99
Answer : A

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

44. The ratio of driving tensions in V-belt drives is __________ flat belt drives.
A. Equal to
B. sin? times more than
C. sin? times less than
D. cosec? times more than
Answer : D

45. In order to remove internal stresses produced by hardening the steel, the process usually adopted is
A. Tempering
B. Normalising
C. Annealing
D. Spheroidising
Answer : A

46. 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

47. Which one of the following loading is considered for the design of axles?
A. Bending moment only
B. Twisting moment only
C. Combined bending moment and twisting moments
D. Combined action of bending moment, twisting moment and axial thrust
Answer : A

48. Castle nut is a locking device in which
A. One smaller nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming
B. A slot is cut partly is middle of nut and then slot reduced by tightening a screw
C. A hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is screwed on the bolt causing a tight grip
D. Through slots are made at top and a cotter pin is passed through these and a hole in the bolt, and cotter pin spitted and bent in reverse direction at other end
Answer : D

49. For same pulley diameters, center distance, belt speed and belt and pulley materials,
A. Open belt drive transmits more power than crossed belt drive
B. Crossed belt drive transmits more power than open belt drive
C. Open and crossed belt drives transmit same power
D. Power transmission does not depend upon open and crossed types of constructions
Answer : B

50. Which one of the following is a positive drive?
A. V-belt drive
B. Rope drive
C. Crossed flat belt drive
D. Chain drive
Answer : D