Multiple choice question for engineering
Set 1
1. 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
Answer
Answer: b [Reason:] θ=(180/π)xMl/GJ where J=πd⁴/32.
2. According to ASME code, maximum allowable shear stress is taken as X% of yield strength or Y% of ultimate strength.
a) X=30 Y=18
b) X=30 Y=30
c) X=18 Y=18
d) X=18 Y=30
Answer
Answer: a [Reason:] ASME Standard. The lesser value is taken among the two.
3. Does ASME Standard take into consideration shock and fatigue factors?
a) Yes
b) No
Answer
Answer: a [Reason:] Moment is multiplied by a number to consider these factors while designing the shaft.
4. Figure 1
The layout of a shaft supported on bearings at A & B is shown. Power is supplied by means of a vertical belt on pulley B which is then transmitted to pulley C carrying a horizontal belt. The angle of wrap is 180’ and coefficient of friction is 0.3. Maximum permissible tension in the rope is 3kN. The radius of pulley at B & C is 300mm and 150mm.
For questions i-iv, refer to figure 1.
4. i. Calculate the torque supplied to the shaft.
a) 453.5N-m
b) 549.3N-m
c) 657.3N-m
d) None of the listed
Answer
Answer: b [Reason:] M=(P₁-P₂)xR where P₁=3000N, P₂=P₁/e^(Coeff of friction x Angle of wrap).
5. ii. Calculate the tension in the rope of pulley C.
a) 6778.3N and 7765.3N
b) 5948.15N and 2288.75N
c) 5468.4N ad 8678.3N
d) None of the listed
Answer
Answer: b [Reason:] (P₃-P₄)x150=549.3×1000 and P₃/P₄=2.6. Hence P₃=5948.15N and P₄=2288.75N.
6. iii. If allowable shear stress in the shaft is 70N/mm² and torsional and bending moments are M=1185000N-mm and m=330000N-mm, find the diameter of the shaft.
a) 36.8mm
b) 39.7mm
c) 44.7mm
d) 40.3mm
Answer
Answer: c [Reason:] 70=(16/πdᵌ)x√M²+m².
7. iv. If bending moment on point B in horizontal plate is M and in vertical plane is m, then the net bending moment at point B is?
a) M
b) m
c) M+m
d) √M²+m²
Answer
Answer: d [Reason:] The two moments act perpendicularly to each other.
8. Calculate the shaft diameter on rigidity basis if torsional moment is 196000N-mm, length of shaft is 1000mm. Permissible angle of twist per meter is 0.5’ and take G=79300N/mm².
a) None of the listed
b) 41.2mm
c) 35.8mm
d) 38.8mm
Answer
Answer: b [Reason:] d⁴=584Ml/Gθ.
9. If yielding strength=400N/mm², the find the permissible shear stress according to ASME standards.
a) 72 N/mm²
b) 76 N/mm²
c) 268 N/mm²
d) 422 N/mm²
Answer
Answer: a [Reason:] 0.18×400.
10. The stiffness of solid shaft is more than the stiffness of hollow shaft with same weight.
a) True
b) False
Answer
Answer: b [Reason:] Hollow shaft is more stiff.
11. The strength of hollow shaft is more than the strength of solid shaft of same weight.
a) True
b) False
Answer
Answer: a [Reason:] Outer fibers are more effective in resisting the applied moments. In hollow shafts material is removed and spread on a larger radius.
12. Solid shaft is costlier than hollow shaft of same weight.
a) True
b) False
Answer
Answer: b [Reason:] Hollow shaft cost is more as material is to be selectively emplaced.
13. Solid shafts are used in epicyclic gearboxes.
a) True
b) False
Answer
Answer: b [Reason:] In epicyclic gears, one shaft rotates inside other and hence hollow shafts are used.
14. Flexible shafts have ___ rigidity in torsion making them flexible.
a) Low
b) High
c) Very high
d) Infinitely small
Answer
Answer: b [Reason:] Flexible shafts have high rigidity in torsion making then capable to transmit torque.
15. Flexible shafts have ______ rigidity in bending moment.
a) High
b) Low
c) Very high
d) Extremely low
Answer
Answer: b [Reason:] Flexible shafts have low rigidity in bending moments making them flexible.
Set 2
1. Which of the following function can the spring perform?
a) Store energy
b) Absorb shock
c) Measure force
d) All of the mentioned
Answer
Answer: d [Reason:] Spring can easily perform all the listed functions.
2. The helix angle is very small about 2⁰. The spring is open coiled spring.
a) Yes
b) It is closed coiled spring
c) That small angle isn’t possible
d) None of the listed
Answer
Answer: b [Reason:] When the helix angle is small, the plane containing each coil is almost at right angles and hence it is called closed coiled spring.
3. The helical spring ad wire of helical torsion spring, both are subjected to torsional shear stresses.
a) True
b) False
Answer
Answer: b [Reason:] The wire of helical torsion sprig is subjected to bending stresses.
4. The longest leaf in a leaf spring is called centre leaf.
a) It is called middle leaf
b) It is called master leaf
c) Yes
d) None of the listed
Answer
Answer: b [Reason:] It is called master leaf.
5. Multi leaf springs are not recommended for automobile and rail road suspensions.
a) True
b) False
Answer
Answer: b [Reason:] They are highly used in automobile and rail road suspensions.
6. The spring index is the ratio of wire diameter to mean coil diameter.
a) True
b) False
Answer
Answer: a [Reason:] It is the ratio of mean coil diameter to wire diameter.
7. If spring index=2.5, what can be concluded about stresses in the wire?
a) They are high
b) They are negligible
c) They are moderate
d) Cannot be determined
Answer
Answer: a [Reason:] If indexis <3 then stresses are high due to curvature effect.
8. A spring with index=15 is prone to buckling.
a) True
b) False
Answer
Answer: a [Reason:] Due to large variation, such a spring is prone to buckling.
9. If the spring is compressed completely and the adjacent coils touch each other,the the length of spring is called as?
a) Solid length
b) Compressed length
c) Free length
d) None of the mentioned
Answer
Answer: a [Reason:] Terminology.
10. If number of coils are 8 and wire diameter of spring 3mm, then solid length is given by?
a) None of the listed
b) 27mm
c) 24mm
d) 21mm
Answer
Answer: c [Reason:] Solid length=8×3.
11. Compressed length is smaller than the solid length.
a) True
b) False
Answer
Answer: b [Reason:] Compressed is length of spring under maximum compressive force. There is some gap between the coils under maximum load.
12. Pitch of coil is defined as axial distance in compressed state of the coil.
a) Yes
b) It is measured in uncompressed state
c) It is same in uncompressed or compressed state
d) None of the listed
Answer
Answer: b [Reason:] Pitch is measured in uncompressed state.
13. If uncompressed length of spring is 40mm and number of coils 10mm, then pitch of coil is?
a) 4
b) 40/9
c) 40/11
d) None of the mentioned
Answer
Answer: b [Reason:] Pitch=Uncompressed length/N-1.
15. Active and inactive, both types of coils support the load although both don’t participate in spring action.
a) Active coils don’t support the load
b) Inactive coils don’t support the load
c) Both active and inactive don’t support the load
d) Both active and inactive support the load
Answer
Answer: b [Reason:] Inactive coils don’t support the load.
Set 3
1. Stress concentration is defined as the localization of high stresses due to irregularities present in the component and no changes of the cross section.
a) True
b) False
Answer
Answer: b [Reason:] The given statement is true apart from the fact that there is no change in the cross section.
2. Stress Concentration Factor is the ratio of nominal stress obtained by elementary equations for minimum cross-section and highest value of actual stress near discontinuity.
a) True
b) False
Answer
Answer: b [Reason:] The stress concentration factor is just the reciprocal of that cited in the question.
3. If a flat plate with a circular hole is subjected to tensile force, then its theoretical stress concentration factor is?
a) 2
b) 3
c) 4
d) 1
Answer
Answer: b [Reason:] For any ellipse, K=1+2 x (semi major axis/semi minor axis).
4. For an elliptical hole on a flat plate, if width of the hole in direction of the load decrease, Stress Concentration Factor will______
a) Increase
b) Decrease
c) Remains constant
d) Can’t be determined. Varies from material to material
Answer
Answer: a [Reason:] K=1+2 x (semi major axis/semi minor axis. Hence K is inversely proportional to the semi minor axis.
5. In which of the following case stress concentration factor is ignored?
a) Ductile material under static load
b) Ductile material under fluctuating load
c) Brittle material under static load
d) Brittle material under fluctuating load
Answer
Answer: a [Reason:] In ductile materials under static load, there is plastic deformation near yielding point and hence redistribution of stresses take place. The plastic deformation is restricted to a smaller area and hence no perceptible damage take place.
6. Is it logical to use fluid analogy to understand the phenomenon of stress concentration?
a) True
b) False
Answer
Answer: a [Reason:] There is a similarity between velocity distribution in fluid flow in a channel and the stress distribution in an axially loaded plate. The equations for flow potential and in fluid mechanics and stress potential in solid mechanics are same.
7. Use of multiple notches in a V shaped flat plate will
a) Reduce the stress concentration
b) Increase the stress concentration
c) No effect
d) Cannot be determined
Answer
Answer: a [Reason:] The sharp bending of a force flow line is reduced due to multiple notches.
8. Which of the following reduces the stress concentration?
a) Use of multiple notches
b) Drilling additional holes
c) Removal of undesired material
d) Each of the mentioned
Answer
Answer: d [Reason:] All the mentioned options reduce the sharp bending of a force flow line.
9. A flat plate 30mm wide and “t”mm wide is subjected to a tensile force of 5kN. The plate has a circular hole of diameter 15mm with the centre coinciding with the diagonal intersection point of the rectangle. If stress concentration factor=2.16, find the thickness of the plate if maximum allowable tensile stress is 80N/mm².
a) 8mm
b) 9mm
c) 10mm
d) 12mm
Answer
Answer: b [Reason:] σ=P/ (w-d) x t or σ=5000/(30-15)xt ; σ(max)=K x σ or σ(max)=2.16 x σ or σ(max)=720/t; Also σ(max)=80.
Set 4
1. Which of the following parameters can be obtained by tension test of a standard specimen?
a) Proportional Limit
b) Yield Strength
c) Percentage Reduction in area
d) All of the mentioned
Answer
Answer:a [Reason:] Tension test determines the parameters related to stress strain curve and also reduction and elongation in area and length can be found respectively.
2. Proportional Limit is defined as the stress at which the stress strain curves begins to deviate from the straight line.
a) True
b) False
Answer
Answer:a [Reason:] Proportional limit is the point of deviation in stress strain curve.
3. Which of the following is the definition of Compliance?
a) Inverse of Rigidity
b) Inverse of Stiffness
c) Proportional to elastic Limit
d) None of the mentioned
Answer
Answer:b [Reason:] Compliance is a parameter which is the inverse of stiffness.
4. Yield strength is defined as the maximum stress at which a marked increase in elongation occurs without increase in________
a) Load
b) Strength
c) Toughness
d) Hardness
Answer
Answer:a [Reason:] Yield strength is the strength at which strain increases. Now as the strength is constant, therefore load is constant.
5. For the materials which do not exhibit a well-defined yield points, the yield strength is defined as the stress corresponding to a permanent set of how much percentage of gauge length?
a) 0.1
b) 0.2
c) 0.3
d) 0.4
Answer
Answer:b [Reason:] Generally for all the practical purpose, an offset of 0.2% of gauge length is considered.
6. Proof strength is defined as the stress which will produce a permanent extension of how much percentage in the gauge length of the standard test specimen.
a) 0.1
b) 0.2
c) 0.3
d) 0.4
Answer
Answer:a [Reason:] Proof strength is used in design of fasteners. It corresponds to 0.1% permanent deformation of gauge length.
7. All engineering materials are plastic.
a) True
b) False
Answer
Answer:a [Reason:] Yes all the existing engineering materials are plastic to some extent.
8. Which of the following are true about plasticity?
a) Permanent Deformation
b) Ability to retain deformation under load or after removal of load
c) Plastic deformation is greater than elastic deformation
d) All of the mentioned
Answer
Answer:d [Reason:] This is the basic definition of plasticity.
9. Which of the following is measure of stiffness?
a) Modulus of elasticity
b) Modulus of plasticity
c) Resilience
d) Toughness
Answer
Answer:a [Reason:] Stiffness is the ability of material to resist deformation under external load. Hence it is measured by modulus of elasticity.
10. Which of the following facts are true for resilience?
a) Ability of material to absorb energy when deformed elastically
b) Ability to retain deformation under the application of load or after removal of load
c) Ability of material to absorb energy when deformed plastically
d) None of the mentioned
Answer
Answer:a [Reason:] Toughness is ability to store energy till proportional limit during deformation and to release this energy when unloaded.
11. Modulus of resilience is defined as
a) Strain energy per unit volume
b) Strain energy per unit area
c) Independent of strain energy
d) None of the mentioned
Answer
Answer:a [Reason:] Modulus of resilience is strain energy per unit volume.
12. Which of the following are true for toughness
a) Ability of material to absorb energy before fracture
b) Measured by Izod & Charpy test
c) Decreases with the increase in temperature
d) All of the mentioned
Answer
Answer:d [Reason:] Toughness is measure of energy stored till fracture occurs. With rise of temperature, molecular bonds weakens and fracture occurs at a lesser load, hence area under stress strain curve decreases.
13. Malleability increases with temperature while ductility decreases with temperature.
a) True
b) False
Answer
Answer:a [Reason:] Malleability is the deformation under compressive load and hence with rise in temperature, the deformation increases and hence malleability increases.
14. Hardness is
a) Surface property
b) Resistance to abrasion
c) Depends upon resistance to plastic deformation of the material
d) All of the mentioned
Answer
Answer:d [Reason:] Hardness is a surface property which is the resistance of material to surface indentation. It depends upon resistance to plastic deformation.
Set 5
1. The shaft is always stepped with ________ diameter at the middle portion and __________ diameter at the shaft ends.
a) Minimum, maximum
b) Maximum, minimum
c) Minimum, minimum
d) Zero, infinity
Answer
Answer: b [Reason:] Maximum diameter is in the middle portion while it is minimum at the ends.
2. ______ is used for a shaft that supports rotating elements like wheels, drums or rope sleaves.
a) Spindle
b) Axle
c) Shaf
d) None of the listed
Answer
Answer: a [Reason:] That is axle and not a spindle.
3. Axle is frequently used in torque transmission.
a) True
b) False
Answer
Answer: b [Reason:] Axle is a shaft supporting rotating elements.
4. Is it necessary for an axle to be ______ with respect to rotating element?
a) Stationary
b) Moving
c) Moving or stationary
d) None of the listed
Answer
Answer: c [Reason:] The axle may be stationary or rotate with the element.
5. Counter shaft is a secondary shaft.
a) True
b) False
Answer
Answer: a [Reason:] It is a secondary shaft used to counter the direction of main shaft.
6. Hot rolling produces a stronger shaft then cold rolling.
a) True
b) False
Answer
Answer: b [Reason:] Cold rolling produces stronger shaft as grain structure isn’t deformed in cold working.
7. Shafts are subjected to ______ forces.
a) Compressive
b) Tensile
c) Shear
d) None of the listed
Answer
Answer: b [Reason:] Shafts are subjected to tensile forces.
8. Which of the following act on shafts?
a) Torsional moment
b) Bending Moment
c) Both torsional and bending
d) None of the mentioned
Answer
Answer: c [Reason:] Shaft is subjected to torsional moment as well as bending moment.
9. When the shaft is subjected to pure bending moment, the bending stress is given by?
a) None of the listed
b) 32M/πdᵌ
c) 16M/πdᵌ
d) 8M/πdᵌ
Answer
Answer: b [Reason:] Stress =My/I where y=d/2 and I=πd⁴/64.
10. 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
Answer
Answer: c [Reason:] Stress=Mr/J where r=d/2 and J=πd⁴/64.