# Design of Machine Elements mcq with answers

Q. 1. The causes of stress concentration are
A : Variations in properties of materials
B : Abrupt change in cross section
C : Discontinuities in components
D : any one of the above

any one of the above

Q. 2. The Number of stress cycles that the standard specimen can complete before
appearance of first fatigue crack is
A : fatigue life
B : endurance limit
C : ultimate strength
D : yield strength

fatigue life

Q. 3. If nominal diameter of screw thread=50mm and pitch=10mm then the mean diameter
of the screw thread will be?
A : 40mm
B : 60mm
C : 55mm
D : 45mm

45mm

Q. 4. A closely-coiled helical spring is acted upon by an axial force. The maximum shear
stress developed in the spring is “T” . Half of the length of the spring is cut off and the
remaining spring is acted upon by the same axial force. The maximum shear stress in the
spring the new condition will be
A : T/2
B : T
C : 2T
D : 4T

T

Q. 5. A self-locking screw has
C : two nuts
D : coefficient of friction more than tangent of lead angle

coefficient of friction more than tangent of lead angle

Q. 6. The key, which fits in the keyway of hub, only is called,
A : sunk key
B : feather key
C : Woodruff key
D : Kennedy key

sunk key

Q. 7. A flanged pipe joint will be a leak-proof joint, if the circumferential pitch of the bolts
is (where d = Diameter of bolt hole)
A : Less than 20d
B : Greater than 30d
C : Between 20d and 30d
D : Equal to inside diameter of pipe

Between 20d and 30d

Q. 8. Stress concentration occurs due to
A : abrupt change in cross-section
B : discontinuities in component
C : internal cracks and flaws
D : any one of the above

any one of the above

Q. 9. A spring used to absorb shocks and vibrations is
A : closely-coiled helical spring
B : open-coiled helical spring
C : conical spring
D : torsion spring

closely-coiled helical spring

Q. 10. A hollow shaft will transmit a __________ torque than a solid shaft of the same mass
and same material.
A : Smaller
B : Greater
C : Medium
D : None of these

Greater

Q. 11. A knuckle joint is used to transmit
A : axial tensile force only
B : axial tensile or compressive force
C : axial compressive force only
D : combined bending and torsional moment

axial tensile force only

Q. 12. Universal coupling is a type of ____
A : Flexible coupling
B : Rigid coupling
C : Both a. and b
D : None of the above

Flexible coupling

screw and nut is provided so as to prevent failure of threads due to
A : direct shear stress
B : torsional shear stress
C : tensile stress
D : compressive stress

direct shear stress

Q. 14. Which of the following materials has maximum ductility
A : grey cast iron
B : mild steel
C : alloy steel
D : high carbon steel

mild steel

Q. 15. When mechanical component is subjected to fluctuating loads, it fails at the stress
which is
A : lower than ultimate tensile strength
B : higher than ultimate tensile strength
C : equal to ultimate tensile strength
D : any value of ultimate tensile strength

lower than ultimate tensile strength

Q. 16. In a steam engine, the valve rod is connected to an eccentric rod by means of
A : Cotter joint
B : Knuckle joint
C : Universal joint
D : Flange coupling

Knuckle joint

Q. 17. Standardization deals with the characteristics of product that include
A : dimensions of machine elements
B : method of testing the product
C : composition and properties of engineering materials
D : all the three

all the three

Q. 18. If the lateral force acting on the set screw is large and tends to displace one part with
respect to other than which point is recommended?
A : Dog Point
B : Cone Point
C : Window Point
D : Cut Point

Dog Point

Q. 19. In a fusion welding process,
A : only heat is used
B : only pressure is used
C : combination of heat and pressure is used
D : none of these

only heat is used

Q. 20. The fulcrum pin of lever is designed on the basis of
A : torsional moment
B : axial tensile force
C : bending moment
D : bearing pressure

bearing pressure

Q. 21. If the stiffness of parts held together by bolt is too large compared with the stiffness
of bolt (hard gasket), then the resultant load on the bolt is equal to
A : initial tension
C : sum of initial tension and external load
D : higher of initial tension and external load

higher of initial tension and external load

Q. 22. If a close-coiled helical spring absorbs 50 N-mm of
energy while extending by 5 mm, its stiffness will be
A : 2 N/mm
B : 4 N/mm
C : 6 N/mm
D : 10 N/mm

10 N/mm

Q. 23. In design of screw jack from buckling considerations, the end conditions are
assumed as
A : both ends are hinged
B : both ends are fixed
C : one end fixed and other hinged
D : one end fixed and other free

one end fixed and other free

Q. 24. When a close-coiled helical spring is subjected to
an axial load, it is said to be under.
A : Bending
B : Shear
C : Torshion
D : Crushing

Torshion

Q. 25. When the helical compression spring is subjected to axial compressive force, the type
of stress induced in the spring wire is,
A : tensile stress
B : compressive stress
C : bending stress
D : torsional shear stress

torsional shear stress

Q. 26. The helix angle in case of closely coiled helical spring is
A : Less than 10°
B : 10° to 15°
C : 15° to 20°
D : More than 20°

Less than 10°

Q. 27. The principle of applying heat and pressure is widely used in
A : spot welding
B : seam welding
C : projection welding
D : all of these

all of these

Q. 28. If friction angle is 30’ then the maximum efficiency of the screw is
A : 0.33
B : 0.66
C : 0.5
D : Noe of the mentioned

0.33

Q. 29. The maximum amplitude of completely reversed stress that the standard specimen
can sustain for 1 million cycles is
A : fatigue life
B : endurance limit
C : ultimate strength
D : yield strength

endurance limit

Q. 30. A spring is defined as a(an) ___ machine element.
A : Plastic
B : Elastic
C : Special purpose
D : both plastic and elastic

Elastic

Q. 31. If core diameter of bolt is 13.8cm the it’s nominal diameter is given by?
A : 17.27mm
B : 15.34mm
C : 14.67mm
D : 16.34mm

17.27mm

Q. 32. When the shaft is subjected to pure torsional moment, the torsional stress is given
by?
A : None of the listed
B : 32M/πdᵌ
C : 16M/πdᵌ
D : 8M/πdᵌ

16M/πdᵌ

Q. 33. If shaft diameter is 40mm, calculate the diameter of sleeves in clamp coupling.
A : 100mm
B : 60mm
C : 40mm
D : 80mm

100mm

Q. 34. The spring in which number of leaves, which are held together by U-clips are called
as
A : Leaf spring
B : semi-elliptical leaf
C : Helical spring
D : elliptical springs

semi-elliptical leaf

Q. 35. Find the Wahl’s factor if spring index is 6.
A : 1.202
B : 1.2424
C : 1.2525
D : 1.5252

1.2525

Q. 36. The laminated springs are given initial curvature
A : To have uniform strength
B : To make it more economical
C : So that plates may become flat, when subjected to design load
D : None of these

So that plates may become flat, when subjected to design load

Q. 37. The angle of twist for a transmission shaft is inversely proportional to
A : shaft diameter
B : (shaft diameter)2
C : (shaft diameter)3
D : (shaft diameter)4

(shaft diameter)4

Q. 38. The spring used in mechanical toys is
A : Leaf spring
B : Spiral spring
C : Helical spring
D : All of these

Spiral spring

Q. 39. Two shafts will have equal strength, if
A : diameter of both the shafts is same
B : angle of twist of both the shafts is same
C : material of both the shafts is same
D : twisting moment of both the shafts is same

twisting moment of both the shafts is same

Q. 40. Value of R40 series is ….
A : 13
B : 16
C : 14
D : 1.12

16

Q. 41. When the shaft is subjected to pure bending moment, the bending stress is given by?
A : 32M/πdᵌ
B : 16M/πdᵌ
C : 8M/πdᵌ
D : M/πdᵌ

32M/πdᵌ

Q. 42. Splines are used if,
A : the power to be transmitted is high
B : the torque to be transmitted is high
C : the speed is high
D : there is relative motion between shaft and hub

there is relative motion between shaft and hub

Q. 43. Maximum principle stress theory is used for
A : cast iron shafts
B : steel shafts
C : flexible shafts
D : plastic shafts

cast iron shafts

Q. 44. If bending stress in a screw is of magnitude 95N/mm² and torsional shear stress of
magnitude 15N/mm², then what is the principal shear stress?
A : 48.7N/mm²
B : 54.3 N/mm²
C : 51.4 N/mm²
D : 49.8 N/mm²

49.8 N/mm²

Q. 45. A right angled bell-crank is designed to raise a load of 5kN at short arm whose
length is 100mm. Also longer arm is of length 500mm. If permissible bearing pressure on pin
is 10N/mm² and diameter of the 20mm, find the length of the pin.
A : 35.5 mm
B : 25.5 mm
C : 20 mm
D : 30 mm

25.5 mm

Q. 46. If shaft diameter is 60mm, how many bolts are recommended for rigid flange
coupling?
A : 2
B : 3
C : 4
D : 5

4

Q. 47. The holding power of sunk key is due to resistance which it offers in
A : Shear
B : Crushing
C : Shear and crushing
D : Tension

Shear and crushing

Q. 48. The bending stress induced in a beam is
A : maximum at the farthest fiber from neutral axis and zero at the neutral axis
B : uniform through out the cross-section
C : zero at the farthest fiber from neutral axis and maximum at the neutral axis
D : zero at the neutral axis and zero at the farthest fiber and maximum at the mean distance

maximum at the farthest fiber from neutral axis and zero at the neutral axis

Q. 49. A spring is designed for
A : Higher strength
B : Higher deflection
C : Higher stiffness
D : highly resistance

Higher deflection

Q. 50. While designing shaft on the basis of torsional rigidity, angle of twist is given by?
A : Ml/Gd⁴
B : 584Ml/Gd⁴
C : 292 Ml/Gd⁴
D : None of the mentioned

584Ml/Gd⁴

Q. 51. If allowable shear stress in the shaft is 48MPa and torsional moments is 254 kNm,
find the diameter of the shaft.
A : 300 mm
B : 200 mm
C : 400 mm
D : 250 mm

300 mm

Q. 52. Find the shear stress in the spring wire used to design a helical compression sprig if a
load of 1200N is applied on the spring. Spring index is 6, and wire diameter 7mm.
A : 452.2N/mm²
B : 468.6N/mm²
C : 512.2N/mm²
D : None of the listed

452.2N/mm²

Q. 53. A right angled bell-crank lever is to be designed to raise a load of 5 kN by applying
3kN Effort. Determine the reaction force acting on fulcrum
A : 8kN
B : 5.83kN
C : 1.66kN
D : 15kN

5.83kN

Q. 54. A railway wagon moving with a speed of 1.5m/s is brought to rest by bumper
consisting of two springs. Mass of wagon is 100kg. The springs are compressed by 125mm.
Calculate the maximum force acting on each spring.
A : 1200N
B : 1500N
C : 1800N
D : 2000N

1200N

Q. 55. What is the output from differential screws when pitch of the two screws is 12mm
and 8mm? Also the nut is rotated by applying a force of 120N at a radius of 300mm and the
two screws remain stationary. The torque of raising and lowering for the two screws is 5k Nmm and 2.5k N-mm where k is the effective axial weight on the screw.
A : 13200 N-mm
B : 15200 N-mm
C : 19200 N-mm
D : 17200 N-mm

19200 N-mm

Q. 56. Find the mean coil diameter of a helical compression sprig if a load of 1200N is
applied on the spring. Spring index is 6, and wire diameter 7mm.
A : 7/6mm
B : 42mm
C : 1200×6/7 mm
D : None of the listed

42mm

Q. 57. If shaft diameter is 40mm, calculate the diameter of hub in flange coupling.
A : 100
B : 120
C : 80
D : 60

80

Q. 58. Two close-coiled helical springs are equal in all respects except the number of turns.
If the number of turns are in the ratio of 2:3, then the stiffness of the spring will be in the
ratio of
A : 08541666666666665
B : 0.1729166666666667
C : 0.12638888888888888
D : 0.37777777777777777

0.12638888888888888

Q. 59. Two spring having stiffness constants of 22N/mm and 25N/mm are connected in
parallel. They are to be replaced by a single spring to have same effect. The stiffness of that
spring will be?
A : None of the mentioned
B : 3N/mm
C : 47N/mm
D : 11.7N/mm

47N/mm

Q. 60. A weighing machine consists of a 2 kg pan resting on a spring in this condition, with
the pan resting on the spring, the length of the spring is 200 mm. When a mass of 20 kg is
placed on the pan, the length of the spring becomes 100 mm. For the spring, the un-deformed
length L and the spring constant K (stiffness) are
A : L=200mm, 1862N/m
B : L=200mm, 1960N/m
C : L=200mm, 19860N/m
D : L=200mm, 2156N/m