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## Machine Design MCQ Set 1

1. The maximum fluctuation of speed is the
a) difference of minimum fluctuation of speed and the mean speed
b) difference of the maximum and minimum speeds
c) sum of the maximum and minimum speeds
d) variations of speed above and below the mean resisting torque line

Answer: b [Reason:] The difference between the maximum and minimum speeds during a cycle is called the maximum fluctuation of speed. The ratio of the maximum fluctuation of speed to the mean speed is called coefficient of fluctuation of speed.

2. The coefficient of fluctuation of speed is the _________ of maximum fluctuation of speed and the mean speed.
a) product
b) ratio
c) sum
d) difference

Answer: b [Reason:] The difference between the maximum and minimum speeds during a cycle is called the maximum fluctuation of speed. The ratio of the maximum fluctuation of speed to the mean speed is called coefficient of fluctuation of speed.

3. In a turning moment diagram, the variations of energy above and below the mean resisting torque line is called
a) fluctuation of energy
b) maximum fluctuation of energy
c) coefficient of fluctuation of energy
d) none of the mentioned

Answer: a [Reason:] The fluctuation of energy may be determined by the turning moment diagram for one complete cycle of operation.The variations of energy above and below the mean resisting torque line are called fluctuation of energy.

4. If E = Mean kinetic energy of the flywheel, CS = Coefficient of fluctuation of speed and Δ E = Maximum fluctuation of energy, then
a) ΔE = E / CS
b) ΔE = E2 × CS
c) ΔE = E × CS
d) ΔE = 2 E × CS

Answer: d [Reason:] ΔE = Maximum K.E. — Minimum K.E. ΔE = 2 E × CS

5. The ratio of the maximum fluctuation of energy to the ……. is called coefficient of fluctuation of energy.
a) minimum fluctuation of energy
b) workdone per cycle
c) maximum fluctuation of energy
d) none of the mentioned

Answer: b [Reason:] The difference between the maximum and the minimum energies is known as maximum fluctuation of energy.

6. Due to the centrifugal force acting on the rim, the flywheel arms will be subjected to
a) tensile stress
b) compressive stress
c) shear stress
d) none of the mentioned

Answer: a [Reason:] The tensile stress in the rim due to the centrifugal force, assuming that the rim is unstrained by the arms, is determined in a similar way as a thin cylinder subjected to internal pressure.

7. The tensile stress in the flywheel rim due to the centrifugal force acting on the rim is given by
a) ρ v2/4
b) ρ v2/2
c) 3ρ v2/4
d) ρ v2

Answer: d [Reason:] Tensile stress = ρ v2

where ρ = Density of the flywheel material, and v = Linear velocity of the flywheel.

8. The cross-section of the flywheel arms is usually
a) elliptical
b) rectangular
c) I-section
d) L-section

Answer: a [Reason:] The cross-section of the arms is usually elliptical with major axis as twice the minor axis.

9. In order to find the maximum bending moment on the arms, it is assumed as a
a) simply supported beam carrying a uniformly distributed load over the arm
b) fixed at both ends
c) cantilever beam fixed at the hub and carrying a concentrated load at the free end of the rim
d) none of the mentioned

Answer: c [Reason:] Due to the torque transmitted from the rim to the shaft or from the shaft to the rim, the arms will be subjected to bending, because they are required to carry the full torque load. In order to find out the maximum bending moment on the arms, it may be assumed as a cantilever beam fixed at the hub and carrying a concentrated load at the free end of the rim.

10. The diameter of the hub of the flywheel is usually taken
a) equal to the diameter of the shaft
b) twice the diameter of the shaft
c) three times the diameter of the shaft
d) four times the diameter of the shaft

Answer: b [Reason:] The diameter of hub is usually taken as twice the diameter of shaft and length from 2 to 2.5 times the shaft diameter. It is generally taken equal to width of the rim.

## Machine Design MCQ Set 2

1. The maximum fluctuation of speed is the
a) difference of minimum fluctuation of speed and the mean speed
b) difference of the maximum and minimum speeds
c) sum of the maximum and minimum speeds
d) variations of speed above and below the mean resisting torque line

Answer: b [Reason:] The difference between the maximum and minimum speeds during a cycle is called the maximum fluctuation of speed. The ratio of the maximum fluctuation of speed to the mean speed is called coefficient of fluctuation of speed.

2. The coefficient of fluctuation of speed is the _____________ of maximum fluctuation of speed and the mean speed.
a) product
b) ratio
c) sum
d) difference

Answer: b [Reason:] The difference between the maximum and minimum speeds during a cycle is called the maximum fluctuation of speed. The ratio of the maximum fluctuation of speed to the mean speed is called coefficient of fluctuation of speed.

3. In a turning moment diagram, the variations of energy above and below the mean resisting torque line is called
a) fluctuation of energy
b) maximum fluctuation of energy
c) coefficient of fluctuation of energy
d) none of the mentioned

Answer: a [Reason:] The fluctuation of energy may be determined by the turning moment diagram for one complete cycle of operation.The variations of energy above and below the mean resisting torque line are called fluctuation of energy.

4. If E = Mean kinetic energy of the flywheel, CS = Coefficient of fluctuation of speed and Δ E = Maximum fluctuation of energy, then
a) ΔE = E / CS
b) ΔE = E2 × CS
c) ΔE = E × CS
d) ΔE = 2 E × CS

Answer: d [Reason:] ΔE = Maximum K.E. — Minimum K.E. = 2 E × CS

5. The ratio of the maximum fluctuation of energy to the ___________ is called coefficient of fluctuation of energy.
a) minimum fluctuation of energy
b) workdone per cycle
c) coefficient of fluctuation of energy
d) none of the mentioned

Answer: b [Reason:] Coefficient of fluctuation of energy is defined as the ratio of the maximum fluctuation of energy to the work done per cycle. It is usually denoted by CE.

6. Due to the centrifugal force acting on the rim, the flywheel arms will be subjected to
a) tensile stress
b) compressive stress
c) shear stress
d) none of the mentioned

Answer: a [Reason:] The following types of stresses are induced in the rim of a flywheel: 1. Tensile stress due to centrifugal force, 2. Tensile bending stress caused by the restraint of the arms, and 3. The shrinkage stresses due to unequal rate of cooling of casting. These stresses may be very high but there is no easy method of determining. This stress is taken care of by a factor of safety.

7. The tensile stress in the flywheel rim due to the centrifugal force acting on the rim is given by
a) ρ v2/4
b) ρ v2/2
c) 3ρ v2/4
d) ρ v2

Answer: d [Reason:] Tensile stress in the flywheel rim due to the centrifugal force = ρ v2

where ρ = Density of the flywheel material, and v = Linear velocity of the flywheel.

8. The cross-section of the flywheel arms is usually
a) elliptical
b) rectangular
c) I-section
d) L-section

Answer: a [Reason:] The cross-section of the arms is usually elliptical with major axis as twice the minor axis, and it is designed for the maximum bending stress.

9. In order to find the maximum bending moment on the arms, it is assumed as a
a) simply supported beam carrying a uniformly distributed load over the arm
b) fixed at both ends (i.e. at the hub and at the free end of the rim) and carrying a uniformly distributed load over the arm.
c) cantilever beam fixed at the hub and carrying a concentrated load at the free end of the rim
d) none of the mentioned

Answer: c [Reason:] Due to the torque transmitted from the rim to the shaft or from the shaft to the rim, the arms will be subjected to bending, because they are required to carry the full torque load. In order to find out the maximum bending moment on the arms, it may be assumed as a centilever beam fixed at the hub and carrying a concentrated load at the free end of the rim.

10. The diameter of the hub of the flywheel is usually taken
a) equal to the diameter of the shaft
b) twice the diameter of the shaft
c) three times the diameter of the shaft
d) four times the diameter of the shaft

Answer: b [Reason:] The diameter of hub is usually taken as twice the diameter of shaft and length from 2 to 2.5 times the shaft diameter. It is generally taken equal to width of the rim.

## Machine Design MCQ Set 3

1. In a four stroke I.C. engine, the turning moment during the compression stroke is
a) positive throughout
b) negative throughout
c) positive during major portion of the stroke
d) negative during major portion of the stroke

Answer: b [Reason:] Since the pressure inside the engine cylinder is less than the atmospheric pressure during the suction stroke, therefore a negative loop is formed. During the compression stroke, the work is done on the gases, therefore a higher negative loop is obtained.

2. The maximum fluctuation of energy is the
a) difference between the maximum and minimum energies
b) sum of the maximum and minimum energies
c) variations of energy above and below the mean resisting torque to the
d) ratio of the mean resisting torque to the workdone per cycle

Answer: a [Reason:] The difference between the maximum and the minimum energies is known as maximum fluctuation of energy.

3. The co-efficient of fluctuation of energy is the ratio of maximum energy to the minimum energy.
a) True
b) False

Answer: b [Reason:] The co-efficient of fluctuation of energy is the ratio of the maximum fluctuation of energy to the work done per cycle.

4. Which of the following statement is wrong?
a) The difference between the maximum and minimum energies is called maximum fluctuation of energy.
b) The co-efficient of fluctuation of speed is the ratio of maximum fluctuation of speed to the mean speed.
c) The variations of energy above and below the mean resisting torque line is known as fluctuation of energy.
d) None of the mentioned

Answer: d [Reason:] All the statements are correct. The difference between the maximum and minimum energies is called maximum fluctuation of energy. The co-efficient of fluctuation of speed is the ratio of maximum fluctuation of speed to the mean speed. The variations of energy above and below the mean resisting torque line is known as fluctuation of energy.

5. The ratio of maximum fluctuation of energy to the workdone per cycle is called
a) fluctuation of energy
b) maximum fluctuation of energy
c) coefficient of fluctuation of speed
d) none of the mentioned

Answer: c [Reason:] The co-efficient of fluctuation of speed is the ratio of maximum fluctuation of speed to the mean speed.

6. Maximum fluctuation of energy in a flywheel is equal to
a) Iω(ω1 – ω2)
b) Iω2CS
c) 2ECS
d) all of the mentioned

7. A flywheel is fitted to the crankshaft of an engine having W as the amount of indicated work per revolution and permissible limits of coefficient of fluctuation of energy and speed as CE and CS respectively. The kinetic energy of the flywheel is given by
a) 2WCE/CS
b) WCE/2CS
c) WCE/CS
d) WCS/2CE

8. If the rotating mass of a rim type flywheel is distributed on another rim type flywheel whose mean radius is half the mean radius of the former, then energy stored in the latter at the same speed will be
a) four times the first one
b) same as the first one
c) one fourth of the first one
d) one and a half times the first one

9. The ratio of maximum fluctuation of speed to the mean speed is called
a) fluctuation of energy
b) maximum fluctuation of energy
c) coefficient of fluctuation of speed
d) none of the mentioned

Answer: c [Reason:] The co-efficient of fluctuation of speed is the ratio of maximum fluctuation of speed to the mean speed.

10. The flywheel of a machine having weight of 4500 N and radius of gyration of 2 m has cyclic fluctuation of speed from 125 r.p.m to 120 r.p.m. Assuming g = 10m/s2, the maximum fluctuation of energy is
a) 12822 N-m
b) 24200 N-m
c) 14822 N-m
d) 12100 N-m

Answer: d [Reason:] Mass of flywheel = weight of flywheel/Acceleration due to gravity = 4500/10kg Moment of Inertia = mk2 = 1800 kgm2

Emax = 1/2 I(?)2 = 12087.2 N-m = 12100 Nm

11. A circular solid disc of uniform thickness 20 mm, radius 200 mm and mass 20 kg, is used as a flywheel. If it rotates at 600 rpm, the kinetic energy of the flywheel, in Joules is
a) 395
b) 790
c) 1580
d) 3160

Answer: b [Reason:] For flywheel K.E = 1/2Iω2 ω = 2πN/60 = 62.83 rad/s

I (for solid circular disk) = 1/2mR2 = 0.4 kg m2 Hence, K.E = 790 Joules.

12. The speed of an engine varies from 210 rad/s to 190 rad/s. During the cycle the change in kinetic energy is found to be 400 Nm. The inertia of the flywheel in kg/m2 is
a) 0.10
b) 0.20
c) 0.30
d) 0.40

Answer: a [Reason:] Given ω1 = 210 rad/ sec, ω2 = 190 rad/ sec, ΔE= 400 Nm As the speed of flywheel changes from ω1 to ω2, the maximum fluctuation of energy,

ΔE = 1/2I [(ω1)22)2] I = 0.10 kgm2

13. For a certain engine having an average speed of 1200 rpm, a flywheel approximated as a solid disc, is required for keeping the fluctuation of speed within 2% about the average speed. The fluctuation of kinetic energy per cycle is found to be 2 kJ. What is the least possible mass of the flywheel if its diameter is not to exceed 1 m ?
a) 40 kg
b) 51 kg
c) 62 kg
d) 73 kg

Answer: b [Reason:] Given N = 1200 rpm, ΔE = 2kJ = 2000 J, D = 1m, Cs = 0.02 Mean angular speed of engine, ω = 2πN/60 = 125.66 rad/ sec

Fluctuation of energy of the flywheel is given by, ΔE = Iω2Cs = 1/2mR2ω2Cs For solid disc I = mR2/2 m = 51 kg

## Machine Design MCQ Set 4

1. The axis of precession is ____________ to the plane in which the axis of spin is going to rotate.
a) parallel
b) perpendicular
c) spiral
d) none of the mentioned

Answer: b [Reason:] The axis of precession is perpendicular to the plane in which the axis of spin is going to rotate. The gyroscopic principle is used in an instrument or toy known as gyroscope.

2. A disc is a spinning with an angular velocity ω rad/s about the axis of spin. The couple applied to the disc causing precession will be
a) 1/2 Iω2
b) Iω2
c) 1/2 Iωωp
d) Iωωp

3. The engine of an aeroplane rotates in clockwise direction when seen from the tail end and the aeroplane takes a turn to the left. The effect of gyroscopic couple on the aeroplane will be
a) to dip the nose and tail
b) to raise the nose and tail
c) to raise the nose and dip of the tail
d) to dip the nose and raise the tail

Answer: c [Reason:] The engine of an aeroplane rotates in clockwise direction when seen from the tail end and the aeroplane takes a turn to the left. The effect of gyroscopic couple on the aeroplane will be to raise the nose and dip of the tail. The engine of an aeroplane rotates in clockwise direction when seen from the tail end and the aeroplane takes a turn to the right. The effect of gyroscopic couple on the aeroplane will be to dip the nose and raise the tail.

4. The engine of an aeroplane rotates in clockwise direction when seen from the tail end and the aeroplane takes a turn to the right. The effect of gyroscopic couple on the aeroplane will be to dip the nose and raise the tail.
a) True
b) False

Answer: a [Reason:] The engine of an aeroplane rotates in clockwise direction when seen from the tail end and the aeroplane takes a turn to the left. The effect of gyroscopic couple on the aeroplane will be to raise the nose and dip of the tail. The engine of an aeroplane rotates in clockwise direction when seen from the tail end and the aeroplane takes a turn to the right. The effect of gyroscopic couple on the aeroplane will be to dip the nose and raise the tail.

5. The steering of a ship means
a) movement of a complete ship up and down in vertical plane about transverse axis
b) turning of a complete ship in a curve towards right or left, while it moves forward
c) rolling of a complete ship side-ways
d) none of the mentioned

Answer: b [Reason:] The steering is the turning of a complete ship in a curve towards right or left, while it moves forward.

6. The rolling of a complete ship side-ways is known as pitching of a ship.
a) True
b) False

Answer: b [Reason:] The pitching is the movement of a complete ship up and down in a vertical plane about transverse axis.

7. The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a left turn. The effect of gyroscopic couple acting on it will be
a) to raise the bow and stern
b) to lower the bow and stern
c) to raise the bow and lower the stern
d) to raise the stern and lower the bow

Answer: c [Reason:] The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a left turn. The effect of gyroscopic couple acting on it will be to raise the bow and lower the stern. The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a right turn. The effect of gyroscopic couple acting on it will be to raise the stern and lower the bow.

8. The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a right turn. The effect of gyroscopic couple acting on it will be to raise the stern and lower the bow.
a) True
b) False

Answer: a [Reason:] The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a left turn. The effect of gyroscopic couple acting on it will be to raise the bow and lower the stern. The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a right turn. The effect of gyroscopic couple acting on it will be to raise the stern and lower the bow.

9. The pitching of a ship is assumed to take place with simple harmonic motion.
a) True
b) False

10. When the pitching of a ship is upward, the effect of gyroscopic couple acting on it will be
a) to move the ship towards star-board
b) to move the ship towards port side
c) to raise the bow and lower the stern
d) to raise the stern and lower the bow

Answer: a [Reason:] When the pitching of a ship is upward, the effect of gyroscopic couple acting on it will be to move the ship towards star-board. When the pitching of a ship is downward, the effect of gyroscopic couple, is to turn the ship towards port side.

## Machine Design MCQ Set 5

1. Power of a governor is the
a) mean force exerted at the sleeve for a given percentage change of speed
b) workdone at the sleeve for maximum equilibrium speed
c) mean force exerted at the sleeve for maximum equilibrium speed
d) none of the mentioned

Answer: d [Reason:] The power of a governor is the work done at the sleeve for a given percentage change of speed. It is the product of the mean value of the effort and the distance through which the sleeve moves. Mathematically, Power = Mean effort × lift of sleeve

2. The effort of a Porter governor is equal to
a) c(m – M)g
b) c(m + M)g
c) C/(m + M)g
d c/(m – M)g

Answer: b [Reason:] The effort of a Porter governor is equal to c(m + M)g. The power of a Porter governor is equal to 4c2/1 + 2c (m + M)gh.

3. The power of a Porter governor is equal to
a) c2/1 + 2c (m + M)gh
b) 2c2/1 + 2c (m + M)gh
c) 3c2/1 + 2c (m + M)gh
d) 4c2/1 + 2c (m + M)gh

Answer: d [Reason:] The effort of a Porter governor is equal to c(m + M)g. The power of a Porter governor is equal to 4c2/1 + 2c (m + M)gh.

4. For the isochronous Porter governor, the controlling force curve is a straight line passing through the origin.
a) True
b) False

Answer: a [Reason:] For the isochronous governor, the controlling force curve is a straight line passing through the origin. The angle φ will be constant for all values of the radius of rotation of the governor.

5. The controlling force diagram for a spring controlled governor is a curve passing through the origin.
a) True
b) False

Answer: b [Reason:] The controlling force diagram for the spring controlled governors is a straight line.

6. A spring controlled governor is said to be unstable when the controlling force
a) increases as the radius of rotation decreases
b) increases as the radius of rotation increases
c) decreases as the radius of rotation decreases
d) remains constant for all radii of rotation

Answer: c [Reason:] If the equilibrium speed of the governor decreases with an increase of the radius of rotation of balls, then the governor is said to be unstable.

7. In a spring controlled governor, when the controlling force _____________ as the radius of rotation increases, it is said to be a stable governor.
a) remains constant
b) decreases
c) increases
d) none of the mentioned

Answer: c [Reason:] For the governor to be stable, in spring controlled governor, the controlling force must increase as the radius of rotation increases. A spring controlled governor is said to be isochronous when the controlling force remains constant for all radii of rotation.

8. A spring controlled governor is said to be isochronous when the controlling force
a) increases as the radius of rotation decreases
b) increases as the radius of rotation increases
c) decreases as the radius of rotation decreases
d) remains constant for all radii of rotation

Answer: d [Reason:] For the governor to be stable, in spring controlled governor, the controlling force must increase as the radius of rotation increases. A spring controlled governor is said to be isochronous when the controlling force remains constant for all radii of rotation.

9. A spring controlled governor is found unstable. It can be made stable by
a) increasing the spring stiffness
b) decreasing the spring stiffness
c) increasing the ball mass
d) decreasing the ball mass