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Multiple choice question for engineering

Set 1

1. Compression Ratio in diesel engine is lesser than that in Spark Ignition engine.
a) True
b) No
c) They are equal
d) Doesn’t matter

View Answer

Answer: b [Reason:] In diesel engine, there is no spark to ignite, charge is compressed to greater extent to support self-ignition.

2. Petrol engine are more economical than diesel engine.
a) True
b) False

View Answer

Answer: b [Reason:] Diesel engine have better thermal efficiency and hence are more economical.

3. There are ____ types of liners.
a) 1
b) 2
c) 3
d) 4

View Answer

Answer: b [Reason:] Dry liners and wet liners.

4. If no re boring allowance is to be given, then thickness of cylinder wall is max pressure is 3.5N/mm², bore diameter=200mm and permissible tensile stress is 40N/mm².
a) 7mm
b) 8mm
c) 9mm
d) 10mm

View Answer

Answer: c [Reason:] t=pD/2σ=8.75mm.

5. If diameter of cylinder of bore is 120mm, then thickness of the cylinder will be
a) Information not sufficient
b) 7mm
c) 12mm
d) 6mm

View Answer

Answer: b [Reason:] t=0.045D + 1.6.

6. If diameter of cylinder bore is 120mm, then thickness of dry liner will be
a) 2.2mm
b) 3.6mm
c) 4.8mm
d) 6mm

View Answer

Answer: b [Reason:] t= 0.03D to 0.035D.

7. If diameter of cylinder bore is 120mm, then thickness of water jacket wall will be
a) 4.26mm
b) 5.25mm
c) 2.56mm
d) All of the listed

View Answer

Answer: d [Reason:] p=t/3 to 3t/4, where t= thickness of cylinder wall=7mm.

8. If diameter of cylinder bore is 120mm, then thickness of water cylinder flange will be
a) 8.8mm
b) 10.2mm
c) 7.8mm
d) 12mm

View Answer

Answer: a [Reason:] q=1.2t to 1.4t.

9. If nominal diameter of bolt used is 20mm, then find the radial distance between outer diameter of flange and pitch circle diameter of studs.
a) 24mm
b) 28mm
c) 32mm
d) 36mm

View Answer

Answer: b [Reason:] r=d+6 to 1.5d i.e. 26mm to 30mm.

10. The circumferential hoop stress and longitudinal stress are both shear stress.
a) True
b) False

View Answer

Answer: b [Reason:] They both are tensile stress.

11. The circumferential hoop stress and longitudinal stress act in same direction and hence are straight away added.
a) True
b) False

View Answer

Answer: b [Reason:] They both act perpendicularly to each other and thus net stress in these directions is reduced.

Set 2

1. Is use of a flywheel recommended when a large motor is required only for a small instant of time?
a) True
b) False

View Answer

Answer: a [Reason:] Fly wheel allows the large motor to be replaced by a smaller motor as the peak power is required only for a small instance of time and not through the entire operation.

2. Flywheels are used in punching and shear operation.
a) True
b) False

View Answer

Answer: a [Reason:] Flywheels store the kinetic energy imparted during idle positions and delivers this energy during actual shearing or punching.

3. Which of the following are functions of flywheel?
a) Store and release energy during work cycle
b) Reduce power capacity of the electric motor
c) Reduce amplitude of speed fluctuations
d) All of the listed

View Answer

Answer: d [Reason:] Flywheel provides uniform motion by storing energy during idle positions and using this at actual operational time and thus reducing the power capacity of the electric motor.

4. When comes down to stress reduction, which one is preferred?
a) Solid flywheel
b) Split flywheel
c) Both have equal stresses
d) Cannot be determined

View Answer

Answer: b [Reason:] The arms are free in split flywheel to contract and hence are better for stress reduction.

5. Flywheel and governor can be interchanged.
a) True
b) False

View Answer

Answer: b [Reason:] Flywheel influences cyclic speed fluctuations while governor control mean speed.

6. If load on the engine is constant, the mean speed will be constant and ___ will not operate.
a) Flywheel
b) Governor
c) Both flywheel and governor
d) None of the mentioned

View Answer

Answer: b [Reason:] Governor is used to control the mean speed and if mean speed is held constant then the governor will not operate.

7. The operation of flywheel is continuous.
a) True
b) False

View Answer

Answer: a [Reason:] Flywheel is used to control the fluctuations and thus is continuously working.

8. Which of the following doesn’t waste energy?
a) Flywheel
b) Governor
c) Both flywheel and governor
d) Neither flywheel nor governor

View Answer

Answer: a [Reason:] Flywheel has kinetic energy which is 100% convertible while governor suffer from friction losses.

9. Which of the following is not true for cast iron flywheels?
a) Excellent damping
b) Cheap
c) Given complex shape
d) Sudden failure

View Answer

Answer: d [Reason:] Due to low tensile strength failure is sudden.

10. When the driving torque is more than load torque, flywheel is ______
a) Accelerated
b) Decelerated
c) Constant velocity
d) Can’t be determined

View Answer

Answer: a [Reason:] I[dω/dt]=Driving torque-load torque.

11. Answer the following in context of this figure
The following is a work cycle graph for a flywheel. T₂ is the torque supplied by motor while T₁ and T₃ are the torques required by machine.

machine-design-questions-answers-flywheel-q11

11. During the portion AB the flywheel is _____
a) Accelerated
b) Decelerated
c) Maintain constant speed
d) None of the listed

View Answer

Answer: a [Reason:] Driving torque is more than the torque supplied by motor.

12. During the portion BC the flywheel is _____
a) Accelerated
b) Decelerated
c) Maintain constant speed
d) None of the listed

View Answer

Answer: a [Reason:] Driving torque is lesser than the torque supplied by motor.

13. The flywheel is accelerated during the
a) AB
b) BC
c) CD
d) Both AB and CD

View Answer

Answer: d [Reason:] Whenever the torque supplied by the motor is greater than the torque needed by machine, flywheel will accelerate.

Set 3

1. The common normal to the curves of the two teeth must not pass through the pitch point.
a) True
b) It must pass
c) It may or may not pass
d) None of the listed

View Answer

Answer: b [Reason:] The common normal must pass through the point where two mating gears meet.

2. Which of the following can be used for power transmission in intersecting shafts.
a) Spur Gear
b) Helical Gear
c) Bevel Gear
d) None of the listed

View Answer

Answer: c [Reason:] Bevel gears are used for power transmission in case of intersecting shafts.

3. Is it possible to transmit power between shafts lying in different planes using gears?
a) Yes
b) No

View Answer

Answer: a [Reason:] Worm or crossed helical gears can be used in this case for power transmission.

4. The two gears are said to have conjugate motion if
a) They have constant angular velocity ratio
b) Variable angular velocity ratio
c) Infinitely small angular velocity ratio
d) None of the mentioned

View Answer

Answer: a [Reason:] Two gear are said to have conjugate motion and tooth profiles are said to have conjugate curves if they have constant angular velocity ratio.

5. Which of the following is not true about gears?
a) Positive drive
b) Constant velocity ratio
c) Transmit large power
d) Bulky construction

View Answer

Answer: d [Reason:] They have compact construction.

6. Gear drive don’t require precise alignment of shafts.
a) True
b) False

View Answer

Answer: b [Reason:] A minute level of misalignment isn’t tolerated in gears.

7. Spur gears can be used only when the two shafts are parallel.
a) True
b) False

View Answer

Answer: a [Reason:] The teeth are cut parallel to the axis of shaft.

8. The teeth of the helical gears are cut parallel to the shaft axis.
a) True
b) False

View Answer

Answer: b [Reason:] They are cut at an angle with the shaft axis.

9. Herringbone gear can be used in
a) Intersecting shafts only
b) Parallel shafts only
c) Both intersection and parallel shafts
d) None of the mentioned

View Answer

Answer: b [Reason:] It consist of two helical gears with the opposite hand of the helix.

10. Bevel gears impose ____ loads on the shafts.
a) Radial and thrust
b) Radial
c) Thrust
d) Neither radial nor thrust

View Answer

Answer: a [Reason:] Bevel gears have the shape of a truncated cone and tooth is cut straight or spiral.

11. Which of the following are true for worm gears?
a) Worm is in the shape of threaded screw
b) Threads on the worm have small lead
c) Worm imposes high thrust loads
d) Characterised by low speed reduction ratio

View Answer

Answer: d [Reason:] They are characterised by high speed reduction ratio.

12. Greater the velocity ratio, smaller the gearbox.
a) True
b) Greater the gearbox
c) Size of gearbox remains unaffected
d) None of the listed

View Answer

Answer: b [Reason:] Greater velocity leads to increase in size of gear wheel which results in size of gearbox.

13. Required velocity ratio is 60:1, which of the following are recommended?
a) Worm
b) Spur
c) Bevel
d) None of the mentioned

View Answer

Answer: a [Reason:] For high speed reduction ratio, worm gears are recommended.

14. For a constant velocity ratio, the common normal to the tooth profile at point of contact must pass through a continuously variable point.
a) True
b) It pass through a fixed point
c) Constant velocity ratio isn’t required, hence variable point is preferred
d) None of the listed

View Answer

Answer: b [Reason:] It must pass through a fixed point called pitch to maintain a constant velocity ratio.

Set 4

1. Thick film lubrication describes a phenomenon where two surfaces are _______ separated.
a) Completely
b) Partially
c) Not
d) None of the mentioned

View Answer

Answer: a [Reason:] There is no contact between the two surfaces.

2. Hydrodynamic bearing is a self-acting bearing.
a) True
b) False

View Answer

Answer: a [Reason:] The pressure in the bearing is created within the system due to rotation of the shaft.

3. A journal bearing is a ______ contact bearing working on the hydrodynamic lubrication and which supports load in____ direction.
a) Sliding, Axial
b) Rolling, Radial
c) Sliding, Radial
d) Rolling, Axial

View Answer

Answer: c [Reason:] This is how journal bearing works. It derives its name from the portion of the shaft inside the bearing.

4. Partial bearing is preferred over journal bearing.
a) True
b) No
c) More friction losses
d) Can’t be determined

View Answer

Answer: a [Reason:] Friction losses are lesser and construction is simple.

5. Temperature rise in partial bearing is ____ than full bearing.
a) Lesser
b) Greater
c) Equal
d) Undeterminable

View Answer

Answer: a [Reason:] Due to lesser friction, temperature rise is less.

6. A clearance bearing is design accurately to keep the radius of journal and bearing equal.
a) Journal radius is kept larger
b) Journal radius is kept smaller
c) True
d) Can’t be determined

View Answer

Answer: b [Reason:] Journal radius is kept smaller.

7. Fitted bearing must be partial bearing.
a) True
b) No
c) No lubricating space is required
d) Can’t be stated

View Answer

Answer: a [Reason:] To provide space for lubricating oil.

8. Footstep bearing is an axial load bearing.
a) True
b) Thrust load
c) Shear load
d) None of the listed

View Answer

Answer: b [Reason:] It is a thrust bearing in which shaft end is in contact with bearing surface.

9. Hydrostatic and hydrodynamic lubrication are the same thing.
a) True
b) False

View Answer

Answer: b [Reason:] In hydrodynamic, motion is provided by the shaft while in hydrostatic the motion is provided by an external source.

10. If we exclude the cost factor, which bearing is preferred?
a) Hydrostatic
b) Hydrodynamic
c) Both are equally preferred
d) Cannot be determined

View Answer

Answer: a [Reason:] High load capacity, no starting friction and no rubbing action.

11. If fluid film pressure is high and surface rigidity is low than mode of lubrication is called as elastohydrodynamic lubrication.
a) True
b) False

View Answer

Answer: a [Reason:] In such cases, elastic deflections of the parts causes development of the film.

Set 5

1. Lewis equation is used to obtain ____ strength of bevel gears.
a) Beam
b) Abrasive
c) Wear
d) Corrosive

View Answer

Answer: a [Reason:] According to Lewis equation, Beam strength=product of module, face width of elemental section, permissible bending stress and Lewis form factor.

2. Beam strength of the bevel gear is independent of the cone distance.
a) True
b) False

View Answer

Answer: b [Reason:] In other form S=mbσY[1- b/A] where A= cone distance.

3. Beam strength indicates the maximum value of the ___________ force at the large end of the tooth that the tooth can transmit without bending.
a) Tangential
b) Radial
c) Axial
d) None of the listed

View Answer

Answer: a [Reason:] Beam strength is analysed by using the pitch radius at the larger end of the tooth.

4. Wear strength of the bevel gear can be calculated by using ________ equation.
a) Buckingham
b) Lewis
c) Newtonian
d) Rayleigh

View Answer

Answer: a [Reason:] Bevel gear is considered to be equivalent to a formative spur gear in a plane which is perpendicular to the large end and hence Buckingham equation is applied.

5. If back cone distance is 10mm, then pitch circle diameter of the formative pinion is given by?
a) 10mm
b) 20mm
c) 5mm
d) 10√2 mm

View Answer

Answer: b [Reason:] PCD=2xr.

6. The wear strength indicates the maximum value of radial force at the large end of the tooth that the tooth can transmit without pitting failure.
a) True
b) False

View Answer

Answer: b [Reason:] It indicates the maximum value of tangential force.

7. If velocity is 5m/s, then velocity factor for a cut teeth is
a) 0.55
b) 0.66
c) 1.55
d) 1.66

View Answer

Answer: a [Reason:] C=6/6+v.

8. If velocity is 5m/s, then velocity factor for generated teeth is
a) 0.71
b) 1.1
c) 0.9
d) 1.71

View Answer

Answer: a [Reason:] C=5.6/5.6+√v.

9. Calculate the ratio factor Q if a pair of bevel gear consist of 25 teeth pinion meshing with a 40 teeth gear.
a) 1.964
b) 1.438
c) 1.554
d) 0.998

View Answer

Answer: b [Reason:] tanϒ=25/40 or ϒ=32⁰. Q=2×40/ [40+25xtan(32)].

10. If surface hardness for a par of bevel gears is 400BHN, then material constant is
a) 3N/mm²
b) 2.56N/mm²
c) 0.98N/mm²
d) 1.44N/mm²

View Answer

Answer: b [Reason:] K=0.16x[BHN/100]².

11. Calculate the wear strength for a pair of bevel gears having face width=20mm, module=5mm, No of teeth on pinion and gear 25 and 40 respectively and PCD of pinion=75mm.
a) 3668.5N
b) 4884.5N
c) 5126.6N
d) 4117.3N

View Answer

Answer: b [Reason:] S=0.75xbxQxDxK/Cos ϒ. Tan ϒ=25/40 or ϒ=32⁰. Q=2×40/ [40+25xtan(32)] K=0.16x[BHN/100]².

12. If service factor is 1.4 & tangential ad dynamic load is 1180N and 1500N respectively, then calculate the effective load.
a) 3662N
b) 2889N
c) 3152N
d) 2236N

View Answer

Answer: c [Reason:] Effective load=1.4×1180 + 1500.