Machine Design MCQ Solved Paper for ISRO Recruitment

1. For a bevel gear having the pitch angle ?, the ratio of formative number of teeth (TE) to actual number of teeth (T) is
A. 1/sin?
B. 1/cos?
C. 1/tan?
D. sin? cos?
Answer : B

2. If a material fails below its yield point, failure would be due to
A. Straining
B. Fatigue
C. Creep
D. Sudden loading
Answer : B

3. 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

4. Yield point in fatigue loading as compared to static loading is
A. Same
B. Higher
C. Lower
D. Depends on other factors
Answer : C

5. The bending stress in a curved beam is
A. Zero at the centroidal axis
B. Zero at the point other than centroidal axis
C. Maximum at the neutral axis
D. None of these
Answer : B

6. Cast iron pipes are mainly used
A. For conveying steam
B. In water and sewage systems
C. In pressure lubrication systems on prime movers
D. All of the above
Answer : B

7. The bearings of heavy series have capacity ________ over the medium series.
A. 20 to 30%
B. 10 to 20%
C. 30 to 40%
D. 40 to 50%
Answer : A

8. 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

9. The ratio of driving tensions for flat belts, neglecting centrifugal tension, is (where T?, and T? = Tensions on the tight and slack sides of belt respectively, ? = Coefficient of friction, between the belt and pulley, and ? = Angle of contact)
A. T?/T? = ??
B. log (T?/T?) = ??
C. T?/T? =e??
D. T?/T? = log ??
Answer : C

10. The constant factor in case of R10 series of preferred numbers is
A. 1.06
B. 1.12
C. 1.26
D. 1.58
Answer : C

11. The velocity factor for ordinary cut gears operating at velocities upto 12.5 m/s is equal to
A. 0.75/ (0.75 + ?v)
B. 3/ (3 + v)
C. 4.5/ (4.5 + v)
D. 6/ (6 + v)
Answer : B

12. Eye bolts are used for
A. Foundation purposes
B. Absorbing shock and vibrations
C. Transmission of power
D. Lifting and transportation of machines and cubicles
Answer : D

13. The velocity factor for very accurately cut and ground metallic gears operating at velocities upto __________ are equal to 6/(6 + v).
A. 10 m/s
B. 12.5 m/s
C. 15 m/s
D. 20 m/s
Answer : D

14. The velocity of sliding ________ the distance of the point of contact from the pitch point.
A. Is directly proportional to
B. Is inversely proportional to
C. Is equal to cos ? multiplied by
D. Does not depend upon
Answer : A

15. A spring of stiffness 1000 N/m is stretched initially by 100 mm from the undeformed position. The work required to stretch it by another 100 mm is
A. 5 N-m
B. 7 N-m
C. 10 N-m
D. 15 N-m
Answer : D

16. The rivet head used for boiler plate riveting is usually
A. Pan Head
B. Snap head
C. Counter sunk head
D. Conical head
Answer : B

17. 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

18. 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

19. The cold working of metals is carried out __________ the recrystallisation temperature.
A. Above
B. Below
C. At
D. None of these
Answer : B

20. 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

21. Rankine's theory of failure is applicable for following type of materials
A. Brittle
B. Ductile
C. Elastic
D. Plastic
Answer : A

22. A connecting rod is designed as a
A. Long column
B. Short column
C. Strut
D. All of these
Answer : C

23. 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

24. Which of the following statement is correct regarding power screws?
A. The efficiency of a self locking screw can not be more than 50%
B. The efficiency of Acme (trapezoidal) thread is less than that of a square thread
C. If the friction angle is less than the helix angle of the screw, then the efficiency will be more than 50%
D. (A) and (B) Only
Answer : D

25. Elastic nut is a locking device in which
A. One small nut is tightened over main nut and main nut tightened against smaller one by loosening, creating friction jamming
B. A slot is cut partly in middle of nut and then slot reduced by tightening a screw
C. Hard fibre or nylon cotter is recessed in the nut and becomes threaded as the nut is stewed 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 splitted and bent in reverse direction at other end
Answer : C

26. The steel pulleys are __________ in weight than cast iron pulleys of the same capacity.
A. Heavier
B. Lighter
C. Moderate
D. None of these
Answer : B

27. If two springs are in parallel then their overall stiffness will be
A. Half
B. Same
C. Double
D. None of the above
Answer : C

28. In cross or regular lay ropes
A. Direction of twist of wires in strands is opposite to the direction of twist of strands
B. Direction of twist of wires and strands are same
C. Wires in two adjacent strands are twisted in opposite direction
D. Wires are not twisted
Answer : A

29. The rolling contact bearings are known as
A. Thick lubricated bearings
B. Plastic bearings
C. Antifriction bearings
D. Thin lubricated bearings
Answer : C

30. 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

31. According to I.B.R., the factor of safety of riveted joint should not be less than
A. 1
B. 2
C. 3
D. 4
Answer : D

32. Two shafts A and B under pure torsion are of identical length and identical weight and are made of the same material. The shaft A is solid and the shaft B is hollow. We can say that
A. Shaft B is better than shaft A
B. Shaft A is better than shaft B
C. Both the shafts are equally good
D. None of these
Answer : A

33. The shearing stresses in the inner face as compared to outer face of the wire in a heavy close coiled spring is
A. Larger
B. Smaller
C. Equal
D. Larger/smaller depending on diameter of spring coil
Answer : A

34. 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

35. In a marine flange coupling, the pitch circle diameter of bolts is taken as
A. 1.2 d
B. 1.6 d
C. 2d
D. 2.5 d
Answer : B

36. 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

37. Jam 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 in 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 spitted and bent in reverse direction at other end
Answer : A

38. The draw of cotter should not be more than
A. 3 mm
B. 6 mm
C. 8 mm
D. 12 mm
Answer : A

39. 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

40. Auto frettage is the method of
A. Joining thick cylinders
B. Calculating stresses in thick cylinders
C. Pre-stressing thick cylinders
D. Increasing the life of thick cylinders
Answer : C

41. 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

42. 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

43. 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

44. The stress which vary from a minimum value to a maximum value of the same nature (i.e. tensile or compressive) is called
A. Repeated stress
B. Yield stress
C. Fluctuating stress
D. Alternating stress
Answer : C

45. An alien bolt is
A. Self locking bolt
B. Same as stud
C. Provided with hexagonal depression in head
D. Used in high speed components
Answer : C

46. When a circular beam of diameter d is subjected to a shear force F, the maximum shear stress induced will be
A. 4F/ ?d²
B. 6F/ ?d²
C. 8F/ ?d²
D. 16F/ 3?d²
Answer : D

47. 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

48. The design of shafts made of brittle materials is based on
A. Guest's theory
B. Rankine's theory
C. St Venant's theory
D. Von Mises theory
Answer : B

49. The process which improves the machinability of steels, but lowers the hardness and tensile strength is
A. Normalising
B. Full annealing
C. Process annealing
D. Spheroidising
Answer : D

50. The ball bearings are provided with a cage
A. To reduce friction
B. To facilitate slipping of balls
C. To prevent the lubricant from flowing out
D. To maintain the balls at a fixed distance apart
Answer : D