Machine Design MCQ (Multiple Choice Questions)

1. In machine design, which of the following joins two rotating shafts to each other?
a) Key
b) Coupling
c) Gear
d) Belt drive

Answer: b
Explanation: Key is a device which joins a machine element to a shaft. Gears and belt drives are devices which are used to transfer power from one shaft to another. Couplings are used to join two rotating shafts.

2. Which of the following is true with respect to hollow and solid shafts in machine design?
a) Hollow shafts are costlier than solid shafts
b) Stiffness of a solid shaft is more than hollow shaft
c) Strength of hollow shaft is less than solid shaft
d) Hollow shafts are cheaper than solid shafts

Answer: a
Explanation: Hollow and solid shafts are two types of shafts that are commonly used. The space required by a hollow shaft is more than solid ones. Stiffness of a hollow shaft is more as compared with solid shaft. Also, strength of hollow shafts are more than solid shafts.

3. Which of the following coupling is used to connect two parallel shafts when they are at a small distance apart?
a) Hooke’s coupling
b) Rigid coupling
c) Muff coupling
d) Oldham’s coupling

Answer: d
Explanation: Hooke’s or universal coupling is used to connect two shafts with intersecting axes, rigid couplings for collinear shafts and oldham’s coupling for shafts which are placed at a small distance apart. Muff coupling is a type of rigid coupling.

4. Which of the following expression is not correct for designing a shaft according to rigidity?
a) T = GθJ / L
b) J = TL / Gθ
c) θ = TL / GJ
d) L = GθT / J

Answer: d
Explanation: According to shaft design on rigidity basis, the following expression is used: T / J = Gθ / L, where J: polar moment of inertia, T: torsional moment, θ: angle of twist, L: length of shaft, G: modulus of rigidity.

5. What are the two types of rigid flange couplings in machine design?
a) Stable and unstable
b) Flexible and non-flexible
c) Protected and unprotected
d) Deformable and non-deformable

Answer: c
Explanation: Rigid flange coupling have flanges and a nut bolt arrangement and cannot tolerate any mis-alignment between shafts and are used to transmit high torques. They are of two types: protected and unprotected type.

6. What will be the diameter of a bolt (in mm), if the total number of bolts is 4 and shaft has a diameter of 10 mm in a flexible coupling?
a) 2
b) 2.5
c) 5
d) 1.25

Answer: b
Explanation: To calculate the diameter of bolt in a flexible coupling, we have, d_b=0.5 d / sqrt N, where, d_b :bolt diameter (mm), N: number of bolts, d: shaft diameter (mm).

7. What will be the Wahl factor, if coil and wire diameters are 60 and 12 mm, respectively?
a) 0.998
b) 1.064
c) 0.752
d) 1.310

Answer: d
Explanation: The spring index is calculated by C = 60 / 12 = 5. Further, the Wahl factor is given by K= (4C-1 / 4C-4) + (0.615 / C), which gives K= 1.310.

8. Which of the following is not the function of a spring in machine design?
a) They are used for the measurement of force and to control motion
b) They are used to absorb shocks and vibrations
c) They are used to store energy
d) They are used to measure displacement

Answer: d
Explanation: Spring is a mechanical device which changes its size under deflection due to the application of force and regains its original size when the load is removed. The functions of a spring are to measure forces such as in spring balance, absorb shocks , and are also used to store energy.

9. Which of the following is not true for rigid and flexible couplings?
a) Rigid couplings are expensive than flexible couplings
b) Flexible couplings can tolerate any slight misalignment between axes of shafts
c) Flexible couplings can absorb shocks and vibrations
d) Rigid couplings cannot tolerate slight misalignment between axes of shafts

Answer: a
Explanation: Rigid couplings are inexpensive as compared to flexible couplings. Flexible couplings are provided with additional safety parts such as bushes to absorb shock and vibrations. Rigid couplings cannot tolerate any misalignment between the axes of shafts.

10. Which of the following materials are subjected to most severe stress concentration?
a) Ductile materials under fluctuating load
b) Brittle materials under static and fluctuating load
c) Brittle materials under fluctuating load
d) Ductile materials under static load

Answer: b
Explanation: The stress concentration effects is most severe in brittle materials due to their inability for plastic deformation. However, in ductile materials, until the material do not reach yield point, there is no stress concentration.

11. In machine design, which of the following is not true for a good coupling?
a) It should be capable for transmitting power from one shaft to another
b) It should keep shafts in proper alignment
c) It should be easy to assemble and disassemble for repair and maintenance
d) If there is small misalignment between the shafts, the coupling cannot transmit power

Answer: d
Explanation: A coupling is a device which is used to connect two shafts rigidly and transmit power from one shaft to another shaft. The requirements of a good coupling is to transmit power even if there is small misalignment, a coupling should be easy to assemble and disassemble for maintenance purpose.

12. Which of the following line is the most economical in machine design?
a) Goodman line
b) Soderberg line
c) Gerber parabola
d) Lagrange line

Answer: c
Explanation: As soderberg line is the most safest line, the cost required to design according to this criteria will be more, followed by goodman line and gerber parabola.

13. Which type of failures does modified goodman line combines?
a) Fatigue and yield
b) Bending and fatigue
c) Yield and bending
d) Fatigue, bending and yield

Answer: a
Explanation: Modified goodman line is a modified version of goodman line. The failure point ‘S_ut’ on mean stress axis is shifted to ‘S_yt’ for the safety of the component with the help of Lagrange’s line which joins ‘S_yt’ on both y and x axes.

14. In machine design, which of the following mechanical device transfers or multiplies load with an application of small effort?
a) Gears
b) Shafts
c) Levers
d) Bearings

Answer: c
Explanation: Levers are mechanical devices in the form a rigid bar which multiplies or transfer the force with a small effort with the help of a fulcrum.

15. Which of the following coupling consists of only sleeve and a key?
a) Muff coupling
b) Flexible coupling
c) Rigid coupling
d) Universal coupling

Answer: a
Explanation: Rigid couplings or flexible coupling have flanges and a nut bolt arrangement. Universal couplings have two intersecting forks, collars, centre block, pins and are used to connect two intersecting shafts. Muff coupling have a sleeve and a key arrangement.

16. Which of the following bearings cannot take radial loads?
a) Taper roller bearing
b) Thrust ball bearing
c) Angular contact bearing
d) Deep groove ball bearing

Answer: b
Explanation: Taper roller bearing, angular contact bearing and deep grove ball bearing can take loads in both the directions, axial as well as in radial. Thrust ball bearing can take only axial loads.

17. Which theory of failure is mostly used for ductile materials in machine design?
a) Maximum principal stress theory
b) Maximum shear stress theory
c) Distortion energy theory
d) Haigh’s theory

Answer: b
Explanation: For brittle materials, maximum principal stress theory is used as brittle components fail by fracture instead of yielding. Further, Haigh’s theory is related with maximum strain energy. For ductile materials, maximum shear stress theory is used as yielding is the failure criterion. Distortion energy theory is also used for ductile materials, only if the components require close dimensional accuracy.

18. Which of the following forms of thread can transmit power in only one direction?
a) Acme threads
b) Trapezoidal threads
c) Square threads
d) Buttress threads

Answer: d
Explanation: Buttress threads have a thread angle of 45 degrees, which are only inclined in one given direction, so the power is transmitted in that direction only. Acme, trapezoidal and square threads can transmit power in either directions.

19. Which of the following line is the safest in machine design?
a) Goodman line
b) Soderberg line
c) Gerber parabola
d) Lagrange line

Answer: b
Explanation: As gerber parabola represents the average of all failure points, the region below and above the parabola is not safe. The region below the goodman line is safe, but the region above it consists of some failure points.There are no failure points below and above the soderberg line, so, it is the safest.

20. In machine design, suppose if load applied ‘P’ becomes zero while lowering the load ‘W’ in the case of a power screw, which of the condition should be correct so that the load applied does not becomes zero ( θ: Angle of inclination of load with respect to horizontal, ϕ: friction angle)?
a) θ > ϕ
b) θ < ϕ
c) θ = ϕ
d) θ ≤ ϕ

Answer: a
Explanation: For lowering the load, we have, P= W tan (θ – ϕ). If load applied becomes zero, then, W ≠ 0 and θ = ϕ. For P ≠ 0, θ > ϕ. If, θ < ϕ, then ‘P’ becomes negative, which is absurd.

21. In machine design, if in a helical spring, load ‘P’ is applied, such that there is total compression, then the corresponding length is known as ?
a) Free length
b) Solid length
c) Compressed length
d) Combined free and solid length

Answer: b
Explanation: If a load is applied such that spring is totally compressed, then there will be negligible distance between corresponding coils. Hence, the length is referred to be as solid length. Free length is the length when no load acts on a spring.

22. Which of the following terms are involved for calculating equivalent torsional moment when a shaft is subjected to fluctuating loads?
a) k_b M_b and M_t k_t
b) Only k_b M_b
c) Only k_t M_t
d) M_b and M_t

Answer: a
Explanation: When a shaft is subjected with fluctuating loads, then the equivalent torsional moment , is given by: sqrt (k_b M_b)² + (k_t M_t)², where k_b and k_t are combined shock and fatigue factor for bending and torsional moments, respectively and M_b and M_t are bending and torsional moments, respectively.

23. In machine design, while calculating the diameter of shaft according to maximum shear stress theory, which of the following diagrams will be mostly needed?
a) Bending moment diagram only
b) Shear force and bending moment diagrams
c) Bending moment and load diagrams
d) Bending moment, shear force and load diagrams

Answer: c
Explanation: To calculate the diameter of shaft according to maximum shear stress theory, the expression is given by, d³ = 16 T / π ζ_max (kbMb)2+(ktMt)2−−−−−−−−−−−−−−−√, ζ_max is mostly known or given, M_t can be directly calculated according to shaft design by rigidity, M_b which is bending moment needs to be calculated according to different loads applied on the system, so, in most cases bending moment and load diagrams are only needed.

24. What will be the value for the equivalent stiffness (K_eq) of a spring system, if two springs are connected in parallel and stiffnesses are 50 and 40 N/m, respectively?
a) 22.22 N/m
b) 90 N/m
c) 10 N/m
d) 5.71 N/m

25. Which of the following elements transfers torque and is only subjected with bending moment?
a) Brake
b) Clutch
c) Axle
d) Belt drive

Answer: c
Explanation: An axle is a machine element which supports rotating elements such as wheels, and is subjected to bending moments due to transverse loads applied on them and transmits torque. An axle can be simply seen in the rear part of a vehicle, supporting rear wheels.

26. Which of the following is a disadvantage of welding?
a) Lighter structures
b) Very rigid joints
c) Greater strength
d) Inspection is easier

Answer: d
Explanation: Welding is simply a process of joining two or more metals by the application of heat and a filler material. They are lighter structures, the strength produced by them is very strong. Inspection is difficult and it requires skilled labour.

27. Which of the following in power screws is the correct equation for torque if the load is lowered ? ( W: Weight in N, θ: Angle of inclination, ϕ: Friction angle)
a) W tan (θ / ϕ)
b) W tan (θ x ϕ)
c) W tan (θ + ϕ)
d) W tan (θ – ϕ)

Answer: d
Explanation: When a torque is applied, the load moves down on the helical path of screw, which is the hypotenuse of triangle, lead the perpendicular distance and circumference the base of the triangle. By resolving the forces acting on the weight, we get, W tan (θ – ϕ).

28. Which of the following designation of bearing is correct for “6004” in machine design?
a) Deep grove medium bearing with a bore diameter of 4 mm
b) Double row angular bearing with a bore diameter of 20 mm
c) Deep grove extra light bearing with a bore diameter of 20 mm
d) Deep grove light bearing with a bore diameter of 4 mm

Answer: c
Explanation: The number “6” signifies the bearing must be a deep grove ball bearing. Further, the second number “0” designates an extra light bearing. According to the rule, if the last two numbers are 04 and above, the corresponding number must be multiplied by 5 to get the required bore diameter.

29. Which is not a possible type of failure in a riveted joint?
a) Crushing failure of the plate
b) Shear failure of rivet
c) Tensile failure of the plate between rivets
d) Shear failure of plate

Answer: d
Explanation: A riveted joint is a type of joint used to join two components or plates with the help of a rivet. The possible failures in the analysis of a riveted joint are mainly shear failure of rivet, crushing failure of the plate, and tensile failure of the plate between rivets.

30. What are the assumptions made by Stribeck to calculate the static load of a bearing?
a) Balls must be flexible
b) Balls may not be equally spaced
c) Balls in upper half do not support any load
d) Balls in upper half support the load

Answer: c
Explanation: For the calculation of static load for a ball and a roller bearing, the assumptions made by Stribeck were: Balls must be rigid and should be equally spaced. Further, the balls should not support any load.

31. What is the requirement to weld a butt joint?
a) The components must lie in the same plane
b) The components may not necessarily lie in the same plane
c) Bevelling is not required for components with a thickness less than 5 mm
d) There is no requirement to weld a butt joint

Answer: a
Explanation: Butt joint is a type of welded joint which is used when the components are placed by their ends are then welded and the two of them must lie in the same plane. Further, bevelling is required if the thickness of a component is less than 5 mm.

32. In machine design, which of the following is true about the roller bearing in comparison with ball bearing?
a) Power lost in friction is more
b) Axial dimensions are less
c) Radial dimensions are more
d) They have point contact

Answer: a
Explanation: Roller bearing is a bearing which uses cylindrical roller in most of the cases. Practically, the area of contact of roller is more as compared to ball, so, the heat lost in friction is more as compared to ball bearing.

33. Which of the following correctly symbolizes a fillet joint?
a) A right angled triangle
b) Two parallel lines with an arc above them
c) A triangle with an arc above it
d) A triangle

Answer: a
Explanation: A square butt designates, two parallel lines with an arc above them. A single V butt designates, a triangle with an arc above it. A simple triangle means a projection and a right angled triangle means a fillet joint.

34. In machine design, what is the number of teeths of worm gear in the following designation “2/20/10/8/150”?
a) 10
b) 20
c) 150
d) 2

Answer: b
Explanation: The number “2” designates the number of teeths of worm, “150” is the center distance between the worm and worm gear, “10” is the diametral quotient and “20” is the required number of teeths of a worm gear.

35. Which of the following is not a type of welding joint?
a) Lap joint
b) Butt joint
c) Tee joint
d) Single strap joint

Answer: d
Explanation: Lap joint is a joint in which welding is done by overlapping two components or plates. It may be of parallel or transverse type. Butt joint is done when two components are placed by their ends and welded. Tee joint is also a type of joint where components are placed perpendicular to each other and then welded at their intersections. Single strap joint is a type of rivet joint.

36. Which of the following is the function of rebound clips in a multi-leaf spring?
a) Helps to share the load from master leaf to graduated leaves
b) Hold all the leaves of the spring
c) Engage the bolts to clamp the leaves
d) Attach a member or component to

Answer: a
Explanation: Bolt holes are used to engage all the bolts for clamping. A central clamp is required to hold all the leaves, an eye for attaching a member and rebound clips to share the load from master to graduated leaves.

37. In machine design, how can be leverage calculated?
a) Load arm / Effort arm
b) Effort / Load
c) Load / Effort
d) Effort arm / Load arm

Answer: d
Explanation: In levers, mainly three terms are used: fulcrum, load and effort. The perpendicular distance from the line of action of load to fulcrum is known as load arm and distance from the line of action of effort to fulcrum is called effort arm. Further, the ratio of load to effort is known as Mechanical advantage and the ratio of effort arm to load arm is called Leverage.

38. In machine design, if the effort is located between the load and fulcrum, which type of lever it is?
a) First type
b) Second type
c) Third type
d) Fourth type

Answer: c
Explanation: If the fulcrum is located between load and effort, it is called first type of lever. If load is located between the fulcrum and effort, then it is of second type and for third class of lever, the effort must be between load and fulcrum.

39. Which of the following is not the cause of stress concentration?
a) Abrupt changes in cross-section
b) Discontinuity in the component
c) Machining scratches
d) Point load applied on the component

Answer: d
Explanation: Stress concentration is the development of high stresses due to changes in cross-section, irregularities and discontinuities in the component, machining scratches, etc which causes the separation of flow lines.

40. In machine design, which of the following straight line joins endurance limit(S_e) on the stress amplitude axis and yield strength (S_yt) on the mean stress axis?
a) Soderberg line
b) Modified goodman line
c) Gerber line
d) Goodman line

Answer: a
Explanation: Gerber line is a parabola joining S_e on stress amplitude (y-axis) and S_ut on mean stress (x-axis). A goodman line is a straight line which joins S_e on y-axis and S_ut on x-axis. A soderberg line is a straight line which joins S_e on y-axis and S_yt on x-axis. A modified goodman line is a combination of lagrange and goodman lines.

41. Which of the following shaft are the integrals or equally spaced lines made on a shaft?
a) Stepped shaft
b) Spline shaft
c) Cam shaft
d) Crankshaft

Answer: b
Explanation: Splines are a type of shaft in which there are equally spaced grooves mainly used to transmit high torque and due to the presence of grooves, the load is shared equally.

42. What is the thickness of components required to weld a V or U joint?
a) Less than 5 mm
b) 5 to 12 mm
c) 12.5 mm
d) Greater than 12.5 m

Answer: b
Explanation: To weld square butt joint, components must be less than 5 mm thick. For double V or U joint, a thickness greater than 12.5 mm is required and for V or U joint thickness requirement is 5 to 12 mm.

43. Which of the following is a dominance of power screw?
a) Large load carrying capacity
b) High efficiency
c) Wear of screw is reduced
d) Mechanical advantage is lowered

Answer: a
Explanation: A power screw is a mechanical device which can be used to lift or lower the heavy loads with the aid of a small effort and also for the transmission of power. It has a large load carrying capacity, simple to design, provides noiseless service. But, it has poor efficiency due to the power lost in friction. Further, due to friction, wear becomes a serious problem and mechanical advantage is increased as the effort applied is less

44. In machine design, if in an eccentrically loaded bolted joint, there are nine bolts and a load ‘P’ is acting with an eccentricity ‘e’, then the primary shear force is given by?
a) P / 4
b) P
c) P / 9
d) P /1

Answer: c
Explanation: An eccentrically loaded bolted joint is an arrangement where a bracket and a load is applied vertically to the far end of bracket. Further, the bracket is connected to a support or wall with the help of bolts. In an eccentrically loaded bolted joint, the primary shear force is calculated by the ratio of load acting to the number of bolts given.

45. Which type of welding uses an oxygen-acetlyene gas?
a) Thermit welding
b) Electric arc welding
c) Gas welding
d) Forge welding

Answer: c
Explanation: In thermit welding, a mould is prepared and then thermit is placed to join the metals. In electric arc, an arc is used to heat and join the parts of metal. Forge welding uses an impact force for joining of metals. In gas welding, oxy-acetylene gas is burned in the presence of a torch to create a pointed flame.

46. Which of the following is not a type of transmission shaft?
a) Crankshaft
b) Countershaft
c) Transmission shaft
d) Line shaft

Answer: a
Explanation: Transmission shaft is a shaft used for the transmission of power from source to an application (eg: a machine). Line shaft and countershaft are the types of transmission shaft. A machine shaft is an integral part of itself. Eg: crankshaft.

47. In machine design, what is the maximum shear stress for a material of ultimate tensile strength (S_ut) with keyway effect according to ASME code?
a) 0.18 S_ut
b) 0.135 S_ut
c) 0.30 S_ut
d) 0.225 S_ut

Answer: b
Explanation: According to ASME code for shaft design, the maximum shear stress for a material of ultimate tensile strength (S_ut) is 0.18 S_ut. Further, with keyway effect, the value is to be reduced by 25 % which gives, 0.18 x 0.75 x S_ut.

48. In machine design, how can the term “Lead” be defined ?
a) Distance between two adjacent threads measured parallel to axis
b) Largest diameter of a screw thread
c) Smallest diameter of a screw thread
d) Distance travelled by the nut when the nut is given motion measured parallel to axis

Answer: d
Explanation: Largest and smallest diameters of a screw thread is known as major and minor diameters, respectively. Pitch is defined as the distance between two adjacent threads measured parallel to the axis of screw thread and lead is the distance travelled by a nut when the nut is given one turn, measured parallel to axis.

49. Which of the following is not the method to reduce stress concentration?
a) Usage of additional notches and holes
b) Usage of fillet radius
c) Usage of additional discontinuities
d) Usage of sharp corners

Answer: d
Explanation: For the reduction of stress concentration, several methods are used like using multiple notches, using additional discontinuities, drilling additional holes. Using fillet radius, to avoid sharp corners. These methods will ultimately smoothen the flow and flow lines will be less deviated.

50. Which of the following is not a type of sunk key?
a) Gib headed key
b) Woodruff key
c) Square key
d) Hollow saddle key

Answer: d
Explanation: A sunk key is a type of key which fits halfway in the shaft and the other half lies in the hub. Further, the main types of sunk keys are square key, rectangular key, gib headed key, woodruff key, parallel sunk key. Hollow saddle key is a type of saddle key.