Multiple choice question for engineering
Set 1
1. The advantages of the V-belt drive over flat belt drive are
a) The V-belt drive gives compactness due to the small distance between the centres of pulleys.
b) The drive is positive, because the slip between the belt and the pulley groove is negligible.
c) Since the V-belts are made endless and there is no joint trouble, therefore the drive is smooth.
d) all of the mentioned
Answer
Answer: d [Reason:] Following are the advantages of the V-belt drive over flat belt drive:
a) The V-belt drive gives compactness due to the small distance between the centres of pulleys.
b) The drive is positive, because the slip between the belt and the pulley groove is negligible.
c) Since the V-belts are made endless and there is no joint trouble, therefore the drive is smooth.
d) It provides longer life, 3 to 5 years.
e) It can be easily installed and removed.
f) The operation of the belt and pulley is quiet.
g) The belts have the ability to cushion the shock when machines are started.
h) The high velocity ratio (maximum 10) may be obtained.
i) The wedging action of the belt in the groove gives high value of limiting ratio of tensions.
2. The disadvantages of the V-belt drive over flat belt drive are
a) The V-belt drive cannot be used with large centre distances.
b) The V-belts are not so durable as flat belts.
c) The construction of pulleys for V-belts is more complicated than pulleys for flat belts.
d) all of the mentioned
Answer
Answer: d [Reason:] Following are the disadvantages of the V-belt drive over flat belt drive :
a) The V-belt drive cannot be used with large centre distances.
b) The V-belts are not so durable as flat belts.
c) The construction of pulleys for V-belts is more complicated than pulleys for flat belts.
d) Since the V-belts are subjected to certain amount of creep, therefore these are not suitable for constant speed application such as synchronous machines, and timing devices.
e) The belt life is greatly influenced with temperature changes, improper belt tension and mismatching of belt lengths.
f) The centrifugal tension prevents the use of V-belts at speeds below 5 m/s and above 50m/s.
3. The advantages of the V-belt drive over flat belt drive are
a) It provides longer life, 3 to 5 years.
b) It can be easily installed and removed.
c) The operation of the belt and pulley is quiet.
d) all of the mentioned
Answer
Answer: d [Reason:] Following are the advantages of the V-belt drive over flat belt drive:
a) The V-belt drive gives compactness due to the small distance between the centres of pulleys.
b) The drive is positive, because the slip between the belt and the pulley groove is negligible.
c) Since the V-belts are made endless and there is no joint trouble, therefore the drive is smooth.
d) It provides longer life, 3 to 5 years.
e) It can be easily installed and removed.
f) The operation of the belt and pulley is quiet.
g) The belts have the ability to cushion the shock when machines are started.
h) The high velocity ratio (maximum 10) may be obtained.
i) The wedging action of the belt in the groove gives high value of limiting ratio of tensions.
4. The disadvantages of the V-belt drive over flat belt drive are
a) Since the V-belts are subjected to certain amount of creep, therefore these are not suitable for constant speed application such as synchronous machines, and timing devices.
b) The belt life is greatly influenced with temperature changes, improper belt tension and mismatching of belt lengths.
c) The centrifugal tension prevents the use of V-belts at speeds below 5 m/s and above 50m/s.
d) all of the mentioned
Answer
Answer: d [Reason:] Following are the disadvantages of the V-belt drive over flat belt drive :
a) The V-belt drive cannot be used with large centre distances.
b) The V-belts are not so durable as flat belts.
c) The construction of pulleys for V-belts is more complicated than pulleys for flat belts.
d) Since the V-belts are subjected to certain amount of creep, therefore these are not suitable for constant speed application such as synchronous machines, and timing devices.
e) The belt life is greatly influenced with temperature changes, improper belt tension and mismatching of belt lengths.
f) The centrifugal tension prevents the use of V-belts at speeds below 5 m/s and above 50m/s.
5. The distance between the hinge centre of a link and the corresponding hinge centre of the adjacent link is called
a) pitch of the chain
b) bush roller chain
c) block chain
d) none of the mentioned
Answer
Answer: a [Reason:] A bush roller chain, consists of outer plates or pin link plates, inner plates or roller link plates, pins, bushes and rollers.
The distance between the hinge centre of a link and the corresponding hinge centre of the adjacent link is called pitch of the chain.
6. Industrial rotors will not have uniform diameter throughout their lengths.
a) True
b) False
Answer
Answer: a [Reason:] Industrial rotors are not uniform, because of fitment of pulleys, gears, belt etc.
7. For cutting multi-start threads, the speed ratio is expressed in terms of the lead of the job thread and lead of the lead screw threads.
a) True
b) False
Answer
Answer: a [Reason:] During multi-start thread cutting operation, speed is reduced to one-third to one-fourth of that in turning operation.
8. Which one of the following is a positive drive?
a) Crossed flat belt drive
b) Rope drive
c) V-belt drive
d) Chain drive
Answer
Answer: d [Reason:] The chains are mostly used to transmit motion and power from one shaft to another, when the centre distance between their shafts is short such as in bicycles, motor cycles, agricultural machinery, conveyors, rolling mills, road rollers etc.
9. The chain drive transmits ____________ power as compared to belt drive.
a) more
b) less
c) equal
d) none of the mentioned
Answer
Answer: a [Reason:] Following are the advantages and disadvantages of chain drive over belt or rope drive:
1. As no slip takes place during chain drive, hence perfect velocity ratio is obtained.
2. Since the chains are made of metal, therefore they occupy less space in width than a belt or rope drive.
3. It may be used for both long as well as short distances.
4. It gives a high transmission efficiency (upto 98 percent).
5. It gives less load on the shafts.
6. It has the ability to transmit motion to several shafts by one chain only.
7. It transmits more power than belts.
8. It permits high speed ratio of 8 to 10 in one step.
9. It can be operated under adverse temperature and atmospheric conditions.
10. The relation between the pitch of the chain (p) and pitch circle diameter of the sprocket (D) is given by
a) p = D sin(900/T)
b) p = D sin(1200/T)
c) p = D sin(1800/T)
d) p = D sin(3600/T)
Answer
Answer: c
11. In order to have smooth operation, the minimum number of teeth on the smaller sprocket, for moderate speeds, should be
a) 15
b) 17
c) 21
d) 25
Answer
Answer: b [Reason:] In order to have smooth operation, the minimum number of teeth on the smaller sprocket or pinion may be taken as 17 for moderate speeds and 21 for high speeds.
12. The speed of the sprocket reduces as the chain pitch _____________ for a given number of teeth.
a) increases
b) decreases
c) remains same
d) none of the mentioned
Answer
Answer: a [Reason:] The r.p.m. of the sprocket reduces as the chain pitch increases for a given number of teeth.
13. The greater angle of articulation will increase the life of the chain.
a) True
b) False
Answer
Answer: b [Reason:] Greater angle of articulation will lead to breaking of chain & reduction in life of the chain.
Set 2
1. The velocity ratio of two pulleys connected by an open belt or crossed belt is
a) directly proportional to their diameters
b) inversely proportional to their diameters
c) directly proportional to the square of their diameters
d) inversely proportional to the square of their diameters
Answer
Answer: b [Reason:] It is the ratio between the velocities of the driver and the follower or driven.
Let d1 = Diameter of the driver,
d2 = Diameter of the follower,
N1 = Speed of the driver in r.p.m., and
N2 = Speed of the follower in r.p.m.
∴ Length of the belt that passes over the driver, in one minute
= π d1.N1
Similarly, length of the belt that passes over the follower, in one minute
= π d2 . N2
Since the length of belt that passes over the driver in one minute is equal to the length of belt that passes over the follower in one minute, therefore
π d1.N1 = π d2 . N2
∴ Velocity ratio, N2/N1 = d1/d2.
2. Two pulleys of diameters d1 and d2 and at distance x apart are connected by means of an open belt drive. The length of the belt is
a) π /2 (d1 + d2) 2x + (d1 + d2)2/4x
b) π /2 (d1 – d2) 2x + (d1 – d2)2/4x
c) π /2 (d1 + d2) 2x + (d1 – d2)2/4x
d) π /2 (d1 – d2) 2x + (d1 + d2)2/4x
Answer
Answer: c
3. In a cone pulley, if the sum of radii of the pulleys on the driving and driven shafts is constant, then
a) open belt drive is recommended
b) cross belt drive is recommended
c) both open belt drive and cross belt drive are recommended
d) the drive is recommended depending upon the torque transmitted
Answer
Answer: b [Reason:] In a cross belt drive, both the pulleys rotate in opposite directions. If sum of the radii of the two pulleys be constant, then length of the belt required will also remain constant, provided the distance between centres of the pulleys remain unchanged.
4. Due to slip of the belt, the velocity ratio of the belt drive
a) decreases
b) increases
c) does not change
d) none of the mentioned
Answer
Answer: a [Reason:] The result of the belt slipping is to reduce the velocity ratio of the system. As the slipping of the belt is a common phenomenon, thus the belt should never be used where a definite velocity ratio is of importance.
5. When two pulleys of different diameters are connected by means of an open belt drive, then the angle of contact taken into consideration should be of the
a) larger pulley
b) smaller pulley
c) average of two pulleys
d) none of the mentioned
Answer
Answer: b
6. The power transmitted by a belt is maximum when the maximum tension in the belt (T) is equal to
a) TC
b) 2TC
c) 3TC
d) 4TC
Answer
Answer: c [Reason:] When the power transmitted is maximum, 1/3rd of the maximum tension is absorbed as centrifugal tension.
T = 3TC
where TC = Centrifugal tension.
7. The velocity of the belt for maximum power is
a) √T/3m
b) √T/4m
c) √T/5m
d) √T/6m
Answer
Answer: a [Reason:] We know that T1 = T– TC and for maximum power TC = T/3
T1 = T – T/3 = 2T/3
the velocity of the belt for the maximum power, v = √T/3m
where m = Mass of the belt in kg per metre length.
8. The centrifugal tension in belts
a) increases power transmitted
b) decreases power transmitted
c) have no effect on the power transmitted
d) increases power transmitted upto a certain speed and then decreases
Answer
Answer: c
9. When the belt is stationary, it is subjected to some tension, known as initial tension. The value of this tension is equal to the
a) tension in the tight side of the belt
b) tension in the slack side of the belt
c) sum of the tensions in the tight side and slack side of the belt
d) average tension of the tight side and slack side of the belt
Answer
Answer: d [Reason:] When the driver starts rotating, it pulls the belt from one side (increasing tension in the belt on this side) and delivers it to the other side (decreasing the tension in the belt on that side). The increased tension in one side of the belt is called tension in tight side and the decreased tension in the other side of the belt is called tension in the slack side.
10. The relation between the pitch of the chain ( p) and pitch circle diameter of the sprocket (d) is given by
a) p = d sin (600/T)
b) p = d sin (900/T)
c) p = d sin (1200/T)
d) p = d sin (1800/T)
Answer
Answer: d [Reason:] It is given by p = d sin (1800/T).
Set 3
1. The bevel gears are used to connect
a) two parallel shafts
b) two intersecting shafts
c) two non intersecting shafts
d) none of the mentioned
Answer
Answer: b [Reason:] Two intersecting shafts are connected by bevel gears and pitch cylinders in spur gears.
2. Bevel gears with shafts angle of 900 are termed as
a) zerol gears
b) angular bevel gears
c) mitre gears
d) hypoid gears
Answer
Answer: c [Reason:] The bevel gears with shaft angle 900 are termed as Mitre gears. The bevel gears with any other shaft angle are termed as angular bevel gears.
3. The bevel gears used for connecting non intersecting shafts are
a) mitre gears
b) hypoid gears
c) spiral bevel gears
d) zerol gears
Answer
Answer: b [Reason:] The bevel gears used for connecting non intersecting shafts are hypoid gears. The bevel gears with shaft angle 900 are termed as Mitre gears.
4. Face width of the bevel gear is usually equal to
a) 10 modules
b) pitch cone radius/3
c) pitch cone radius/2
d) none of the mentioned
Answer
Answer: b [Reason:] For correctly designed gears the face width should not be more than 1/3 the slant length, i.e. pitch cone radius.
5. Formative number of teeth on bevel gears is equal to
a) 2 x actual number of teeth
b) actual number of teeth/ cosɸ
c) actual number of teeth/cosα
d) actual number of teeth/cosϴ
Answer
Answer: d
6. Lewis Equation for bevel gear is corrected for
a) variation in p.c.d.
b) variation in tooth thickness
c) taking care of axial thrust
d) variation in torque acting on the tooth
Answer
Answer: a [Reason:] As radius of bevel gear varies along the width, the torque does not produce the same tangential force.
7. Ratio factor Q in wear load equation of bevel gear is given by
a) 2gear ratio G/G + 1
b) 2ratio of formative number of teeth of gear and pinion G
c) G + 1/G‘ +1
d) 2G‘/G
Answer
Answer: b
8. Bevel factor should not be less than
a) 0.75
b) 0.8
c) 0.67
d) 0.76
Answer
Answer: c
9. Pitch cone angle of pinion of straight tooth bevel gear pair with ratio 1.732 is
a) 250
b) 300
c) 600
d) none of the mentioned
Answer
Answer: c
10. The face width of the bevel gear is 0.3 times the radius of pitch cone. Here the bevel factor must be
a) 1.3
b) 3
c) 0.7
d) 1.7
Answer
Answer: c [Reason:] Face width = Pitch cone radius/3
therefore, bevel factor = 0.7.
11. Interchangibility is possible only in
a) bevel gear
b) helical gear
c) spur gear
d) mitre gear
Answer
Answer: c [Reason:] Spur gears are connected by pitch cylinders and therefore, they can interchange.
Set 4
1. In S.H.M., acceleration is proportional to
a) velocity
b) displacement
c) rate of change of velocity
d) none of the mentioned
Answer
Answer: b [Reason:] The acceleration is proportional to its displacement from its mean position.
2. In S.H.M., the velocity vector w.r.t. displacement vector
a) leads by 900
b) lags by 900
c) leads by 1800
d) none of the mentioned
Answer
Answer: a
3. A body having moment of inertia of 30 kg m2 is rotating at 210 RPM and mashes with another body at rest having M.I. of 40 kg m2. The resultant speed after meshing will be
a) 90 RPM
b) 100 RPM
c) 80 RPM
d) none of the mentioned
Answer
Answer: a [Reason:] Since moment is conserved, there fore,
30 x 210 = 40 x Resultant speed
or, Resultant speed = 90 RPM.
4. Inertia force acts
a) perpendicular to the accelerating force
b) along the direction of accelerating force
c) opposite to the direction of accelerating force
d) none of the mentioned
Answer
Answer: c
5. The frequency of oscillation at moon compared to earth will be
a) 6 times more
b) 6 times less
c) 2.44 times more
d) 2.44 times less
Answer
Answer: d [Reason:] Frequency = 1/2π√g/l
since on moon gravitational force g becomes 1/6g
therefore, frequency = 2.44 times less.
6. Polar moment of inertia(IP) of a circular disc is to be determined by suspending it by a wire and noting the frequency of oscillations(f)
a) IP ∞ f
b) IP ∞ f2
c) IP ∞ 1/f2
d) none of the mentioned
Answer
Answer: c
7. The frequency of oscillation of a bigger diameter cylinder compared to a small cylinder inside a cylinder concave surface will be
a) less
b) more
c) same
d) none of the mentioned
Answer
Answer: b [Reason:] The frequency of oscillation of a bigger diameter cylinder compared to a small cylinder inside a cylinder concave surface will be more.
The frequency of oscillation of a cylinder inside a cylinder inside a cylindrical concave surface of bigger radius compared to a small radius will be less.
8. The frequency of oscillation of a cylinder inside a cylinder inside a cylindrical concave surface of bigger radius compared to a small radius will be
a) less
b) more
c) same
d) none of the mentioned
Answer
Answer: a [Reason:] The frequency of oscillation of a bigger diameter cylinder compared to a small cylinder inside a cylinder concave surface will be more.
The frequency of oscillation of a cylinder inside a cylinder inside a cylindrical concave surface of bigger radius compared to a small radius will be less.
9. If the radius of gyration of a compound pendulum about an axis through c.g. is more, then its frequency of oscillation will be
a) less
b) more
c) same
d) none of the mentioned
Answer
Answer: a [Reason:] The frequency of oscillation of a bigger diameter cylinder compared to a small cylinder inside a cylinder concave surface will be more.
The frequency of oscillation of a cylinder inside a cylinder inside a cylindrical concave surface of bigger radius compared to a small radius will be less.
10. The Bifilar suspension method is used to determine
a) natural frequency of vibration
b) position of balancing weights
c) moment of inertia
d) none of the mentioned
Answer
Answer: c
11. The natural frequency of a spring-mass system on earth is ωn. The natural frequency of this system on the moon (gmoon =gearth/6) is
a) ωn
b) 0.408ωn
c) 0.204ωn
d) 0.167ωn
Answer
Answer: a [Reason:] We know natural frequency of a spring mass system is,
ωn = √k/m ………………….(i)
This equation (i) does not depend on the g and weight (W = mg)
So, the natural frequency of a spring mass system is unchanged on the moon.
Hence, it will remain ωn , i.e. ωmoon =ωn.
12. An automotive engine weighing 240 kg is supported on four springs with linear characteristics. Each of the front two springs have a stiffness of 16MN/m while the stiffness of each rear spring is 32MN/m. The engine speed (in rpm), at which resonance is likely to occur, is
a) 6040
b) 3020
c) 1424
d) 955
Answer
Answer: a [Reason:] Given k1 = k2 = 16MN/m, k3 = k4 = 32MN/m, m = 240 kg
Here, k1 & k2 are the front two springs or k3 and k4 are the rear two springs.
These 4 springs are parallel, So equivalent stiffness
keq = k1 + k2 + k3 + k4 = 16 + 16 + 32 + 32 = 96MN/m2
We know at resonance
ω = ωn = √k/m
2πN/60 = √keq/m N =Engine speed in rpm
N = 60/2π√keq/m
= 60/2π√96 x 106/240
= 6040 rpm.
13. A vehicle suspension system consists of a spring and a damper. The stiffness of the spring is 3.6 kN/m and the damping constant of the damper is 400 Ns/m. If the mass is 50 kg, then the damping factor (d ) and damped natural frequency (fn), respectively, are
a) 0.471 and 1.19 Hz
b) 0.471 and 7.48 Hz
c) 0.666 and 1.35 Hz
d) 0.666 and 8.50 Hz
Answer
Answer: a [Reason:] Given k = 3.6 kN/m, c = 400 Ns/m, m = 50 kg
We know that, Natural Frequency
ωn = √k/m = 8.485 rad/ sec
And damping factor is given by,
d or ε = c/cc
= 0.471
Damping Natural frequency,
ωd = √1 – ε2ωn
2πfd = √1 – ε2ωn
fd = 1.19 Hz.
14. For an under damped harmonic oscillator, resonance
a) occurs when excitation frequency is greater than undamped natural frequency
b) occurs when excitation frequency is less than undamped natural frequency
c) occurs when excitation frequency is equal to undamped natural frequency
d) never occurs
Answer
Answer: c [Reason:] For an under damped harmonic oscillator resonance occurs when excitation frequency is equal to the undamped natural frequency
ωd = ωn.
15. A vibratory system consists of a mass 12.5 kg, a spring of stiffness 1000N/m , and a dash-pot with damping coefficient of 15 Ns/m.The value of critical damping of the system is
a) 0.223 Ns/m
b) 17.88 Ns/m
c) 71.4 Ns/m
d) 223.6 Ns/m
Answer
Answer: d [Reason:] Given m= 12.5 kg, k= 1000N/m, c= 15 Ns/m
Critical Damping,
cc = 2m√k/m = 2√km
On substituting the values, we get
cc = 223.6 Ns/m.
Set 5
1. A side and face cutter 125 mm diameter has 10 teeth. It operates at a cutting speed of 14 m/min with a table traverse 100 mm/min. The feed per tooth of the cutter is
a) 10 mm
b) 2.86 mm
c) 0.286 mm
d) 0.8 mm
Answer
Answer: c [Reason:] пDN = 14,
N = 14000/3.14 x 125 = 35.65
Feed for tooth = table traverse/ N x no. of teeth = 100/35.65 x 10 = 0.286 mm.
2. Consider the following statements in case of reverted gear train:
1. The direction of rotation of the first and the last gear is the same.
2. the direction of rotation of the first and the last gear is opposite.
3. The first and the last gears are on the same shaft.
4. The first and the last gears are on separate but co-axial shafts.
Which of these statements is/are correct?
a) 1 and 3
b) 2 and 3
c) 2 and 4
d) 4 alone
Answer
Answer: d [Reason:] Only fourth statement is correct.
3. The dynamic load on a gear is due to
1. inaccurancies of tooth spacing
2. irregularities in tooth profile
3. deflection of the teeth under load
4. type of service
Which of the above statements are correct?
a) 1,2 and 3
b) 2,3 and 4
c) 1,3 and 4
d) 1,2 and 4
Answer
Answer: a [Reason:] The dynamic load on a gear is due to
1. inaccurancies of tooth spacing
2. irregularities in tooth profile
3. deflection of the teeth under load.
4. Consider the following statements:
A 200 stub tooth system is generally preferred in spur gears as it results in
1. stronger teeth
2. lesser number of teeth on the pinion
3. lesser chances of surface fatigue failure
4. reduction of interference
Which of the above statements are correct?
a) 1,2 and 4
b) 3 and 4
c) 1 and 3
d) 1,2,3 and 4
Answer
Answer: a [Reason:] A 200 stub tooth system is generally preferred in spur gears as it results in
1. stronger teeth
2. lesser number of teeth on the pinion
3. reduction of interference.
5. An involute rack with 200 pressure angle meshes with a pinion of 14.50 pressure angle.
a) True
b) False
Answer
Answer: b [Reason:] Such a matching is impossible.
6. When a pair of spur gears of the same material is in mesh, the design is based on pinion.
a) True
b) False
Answer
Answer: a [Reason:] For a pair of gears of the same material in mesh, the strength factor of the pinion is less than that of the gear.
7. Consider the following modifications regarding avoiding the interference between gears:
1. The centre distance between meshing gears be increased
2. Addendum of the gear be modified
3. Teeth should be undercut slightly at the root
4. Pressure angle should be increased
5. Circular pitch be increased
Which of these are effective in avoiding interference?
a) 1,2 and 3
b) 2,3,4 and 5
c) 1,4 and 5
d) 3,4 and 5
Answer
Answer: a
8. In a reverted gear train, two gears P and Q are meshing, Q-R is a compound gear, and R and S are meshing. The modules of P and R are 4 mm and 5 mm respectively. The numbers of teeth in P, Q and r are 20, 40 and 25 respectively. The number of teeth in S is
a) 23
b) 35
c) 50
d) 53
Answer
Answer: a [Reason:] C = 1/2m1(zp + zq) = 1/2m2(zr + zs)
4(20 + 40) = 5(25 + zs)
zs = 23.
9. When two spur gears having involute profiles on their teeth engage, the line of action is tangential to the
a) pitch circles
b) dedendum circles
c) addendum circles
d) base circles
Answer
Answer: a
10. If the annular wheel of an epicyclic gear train has 100 teeth and the planet wheel has 20 teeth, the number of teeth on sun wheel is
a) 80
b) 60
c) 40
d) 20
Answer
Answer: b [Reason:] 2dp + ds = da
2zp + zs = za
2 x 20 + zs = 100
zs = 60.