1000+ Machine Design Multiple Choice Question Answer [Solved]

1. 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

2. The connecting rod bolts are tightened up with initial tension greater than the external load so that
A. Joint may not open up
B. Bolts are weakest elements
C. The resultant load on the bolt would not be affected by the external cyclic load
D. Bolts will not loosen during service
Answer : C

3. Multiple threads are used to secure
A. Low efficiency
B. High efficiency
C. High load lifting capacity
D. High mechanical advantage
Answer : B

4. If the size of a standard specimen for a fatigue testing machine is increased, the endurance limit for the material will
A. Have same value as that of standard specimen
B. Increase
C. Decrease
D. None of these
Answer : C

5. The number of slots in a 25 mm castle nut is
A. 8
B. 6
C. 4
D. 2
Answer : A

6. A locking device in which the bottom cylindrical portion is recessed to receive the tip of the locking set screw, is called
A. Ring nut
B. Castle nut
C. Sawn nut
D. Jam nut
Answer : A

7. 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

8. When a bolt is subjected to shock loading, the resilience of the bolt should be considered in order to prevent breakage at the
A. Thread
B. Middle
C. Shank
D. Head
Answer : A

9. In designing a connecting rod, it is considered like __________ for buckling about Y-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 : B

10. Wahl's stress factor __________ very rapidly as the spring index decreases.
A. Increases
B. Decreases
C. Remain same
D. None of these
Answer : A

11. 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

12. 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

13. In most machine members, the damping capacity of the material should be
A. Low
B. Zero
C. High
D. Could be anything
Answer : C

14. A 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. Is provided with pointed threads
Answer : A

15. 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

16. 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

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

18. In a gear, having Involute teeth, the normal to the Involute is a tangent to the
A. Base circle
B. Pitch circle
C. Addendum circle
D. Dedendum circle
Answer : A

19. Idler pulley is used for
A. Increasing velocity ratio
B. For applying tension
C. Changing the direction of motion of belt
D. All of these
Answer : B

20. When an open coiled helical compression spring is subjected to an axial compressive load, the maximum shear stress induced in the wire is (where D = Mean diameter of the spring coil, d = Diameter of the spring wire, K = Wahl's stress factor, and W = Axial compressive load on the spring)
A. (WD/ ?d³) × K
B. (2WD/ ?d³) × K
C. (4WD/ ?d³) × K
D. (8WD/ ?d³) × K
Answer : D

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

22. 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

23. 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

24. 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

25. Antifriction bearings are
A. Sleeve bearings
B. Hydrodynamic bearings
C. Thin lubricated bearings
D. None of the above
Answer : D

26. A plate with an elliptical hole in the centre, with semi-major axis (A) perpendicular to the direction of loading and semi-minor axis (b) along the direction of loading, is subjected to a pull P. The maximum stress induced at the edge of the hole is equal to (where ? = Stress for a plate with no hole i.e. nominal stress)
A. ? [1 + (b/2a)]
B. ? [1 + (2a/b)]
C. ? [1 + (b/3a)]
D. ? [1 + (3a/b)]
Answer : B

27. Fabric belts are used in industrial applications because
A. They are cheap
B. They can work at high temperature
C. They are unaffected by moisture and humidity
D. None of the above
Answer : A

28. Brittle coating technique is used for
A. Determining brittleness
B. Protecting metal against corrosion
C. Protecting metal against wear and tear
D. Experimental stress analysis
Answer : D

29. The shear stress at a point in a shaft subjected to a torque is
A. Directly proportional to the polar moment of inertia and to the distance of the point from the axis
B. Directly proportional to the applied torque and inversely proportional to the polar moment of inertia
C. Directly proportional to the applied torque and the polar moment of inertia
D. Inversely proportional to the applied torque and the polar moment of inertia
Answer : B

30. The lower deviation is the algebraic 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

31. 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

32. When two non-parallel or intersecting but coplanar shafts are connected by gears, the arrangement is known as,
A. Bevel gearing
B. Helical gearing
C. Worm gearing
D. None of these
Answer : A

33. According to maximum shear stress theory, the maximum shear stress in the shaft is
A. (1/2) × ?(?² + 4?²)
B. ?(?² + 4?²)
C. (1/2) × [? + ?(?² + 4?²)]
D. ? + ?(?² + 4?²)
Answer : A

34. According to Indian standards, a bolt thread of 6 mm size of coarse pitch and with allowance on the threads and normal tolerance grade is designated as
A. M6
B. M8
C. M6 - 8d
D. M8 - 6d
Answer : C

35. The material generally used for aircraft components is
A. Mild steel
B. High speed steel
C. Stainless steel
D. Aluminium
Answer : D

36. In helical gears, the distance parallel to the axis, between similar faces of adjacent teeth, is called
A. Normal pitch
B. Axial pitch
C. Diametral pitch
D. Module
Answer : B

37. 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

38. In testing a material for endurance strength, it is subjected to
A. Static load
B. Dynamic load
C. Impact load
D. Completely reversed load
Answer : D

39. 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

40. 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

41. For tight leakage joints, following type of thread is best suited
A. Metric
B. Buttress
C. Square
D. NPT (national pipe threads)
Answer : D

42. The included angle in unified of American National threads is
A. 60°
B. 55°
C. 47°
D. 29°
Answer : A

43. Which of the following statement is wrong?
A. The V-belt may be operated in either direction with tight side of the belt at the top or bottom
B. The V-belt drive is used with large centre distance
C. The power transmitted by V-belts is less than flat belts for the same coefficient of friction, arc of contact and allowable tension in the belts
D. The ratio of driving tensions in V-belt drive is more than flat belt drives
Answer : B

44. A sliding bearing which can support steady loads without any relative motion between the journal and the bearing, is called
A. Hydrostatic lubricated bearing
B. Hydrodynamic lubricated bearing
C. Boundary lubricated bearing
D. Zero film bearing
Answer : A

45. 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

46. The stress in the threaded part of the bolt will be __________ as compared to the shank.
A. Same
B. Higher
C. Lower
D. None of these
Answer : B

47. The ball bearings are, usually, made from
A. Low carbon steel
B. High carbon steel
C. Medium carbon steel
D. High speed steel
Answer : C

48. Tearing resistance required to tear off the plate per pitch length is (where p = Pitch of rivets, d = Dia. of rivet hole, and ?t = Permissible tensile stress for plate material)
A. p.d.?_t
B. p.t.?_t
C. (p - d) ?_t
D. (p - d) t.?_t
Answer : D

49. The number of slots in a 25 mm castle nut is
A. 8
B. 4
C. 2
D. 6
Answer : D

50. The endurance or fatigue limit is defined as the maximum value of the stress which a polished standard specimen can withstand without failure, for infinite number of cycles, when subjected to
A. Static load
B. Dynamic load
C. Static as well as dynamic load
D. Completely reversed load
Answer : D