160+ Dynamics of Machines Solved MCQs

1.

Which of the following is incorrect regarding inertia force?

A. imaginary force
B. acts upon a rigid body
C. brings the body to equilibrium
D. same direction as of accelerating force
Answer» D. same direction as of accelerating force
2.

Inertia torque acts in the same direction as the accelerating couple?

A. true
B. false
Answer» B. false
3.

If a force has a line of action at a distance h from the centre of gravity, then the value of h is given by            

A. i. α/f
B. i. α/m.g
C. i/m.k
D. m.k/i
Answer» A. i. α/f
4.

D-Alembert’s principle is used for which of the following?

A. change static problem into a dynamic problem
B. change dynamic problem to static problem
C. to calculate moment of inertia of rigid bodies
D. to calculate angular momentum of a system of masses
Answer» B. change dynamic problem to static problem
5.

2 D ALEMBERT'S PRINCIPLE - DYNAMIC ANALYSIS IN RECIPROCATING ENGINES

A. reversed effective force
B. net force
C. coriolis force
D. resultant force
Answer» A. reversed effective force
6.

Why the inertia torque acts in the opposite direction to the accelerating couple?

A. bring the body in equilibrium
B. to reduce the accelerating torque
C. acts as a constraint torque
D. increase the linear acceleration
Answer» A. bring the body in equilibrium
7.

A body remains in equilibrium if                  

A. inertia force is applied in the same direction to the resultant force
B. inertia force is applied in the direction opposite to the resultant force
C. inertia force is applied in the direction perpendicular to the resultant force
D. inertia force is applied in the direction parallel to the resultant force
Answer» B. inertia force is applied in the direction opposite to the resultant force
8.

Inertia force and the reversed effective force are the same.

A. true
B. false
Answer» A. true
9.

In the following picture the G is the center of gravity, the quantity h is known as the “offset”. I is the moment of inertia and k is the radius of gyration. Offset’s value is given by?

A. i.α/f
B. i.α/m.g
C. i/m.k
D. m.k/i
Answer» A. i.α/f
10.

Considering a four bar chain with each link having linear and angular acceleration, applying D-Alembert’s principle will never result in which of the following member?

A. 2- force member
B. 3- force member
C. 4 – force member
D. non accelerating member
Answer» A. 2- force member
11.

The net force acting on the crosshead pin is known as                      

A. crank pin effort
B. crank effort
C. piston effort
D. shaft effort
Answer» C. piston effort
12.

Piston effort acts along the line of stroke.

A. true
B. false
Answer» A. true
13.

In a horizontal engine, reciprocating parts are accelerated when the piston moves from

A. tdc to bdc
B. bdc to tdc
C. midway to tdc
D. bdc to midway
Answer» A. tdc to bdc
14.

In a horizontal engine, reciprocating parts are retarded when the piston moves from

A. tdc to bdc
B. bdc to tdc
C. midway to tdc
D. bdc to midway
Answer» B. bdc to tdc
15.

When the piston is accelerated, the piston effort is given by which of the following the equation?

A. f(l) – f(i)
B. f(l) + f(i)
C. f(l) ± f(i)
D. f(l) – f(i) + r(f)
Answer» B. f(l) + f(i)
16.

In the presence of frictional resistance, the expression for piston effort is                    

A. f(l) – f(i)
B. f(l) + f(i)
C. f(l) ± f(i) – r(f)
D. f(l) – f(i) + r(f)
Answer» C. f(l) ± f(i) – r(f)
17.

Crank effort is the product of crank pin radius and                

A. thrust on sides
B. crankpin effort
C. force acting along connecting rod
D. piston effort
Answer» B. crankpin effort
18.

In a horizontal engine, the weight of the reciprocating parts also add/subtract to the piston effort.

A. true
B. false
Answer» B. false
19.

For the given data of an Internal combustion engine : Mass of parts = 180 kg bore = 175 mm, length of stroke = 200 mm, engine speed = 500 r.p.m., length of connecting rod = 400 mm and crank angle = 60° from T.D.C, find the inertia force.

A. 17.56 n
B. 19.2 n
C. 18.53 n
D. 18.00 n
Answer» C. 18.53 n
20.

45 N/mm2. The connecting rod length between centres is 1.2 m and the cylinder bore is 0.5 m. If the engine runs at 250 r.p.m. and if the effect of piston rod diameter is neglected, calculate the net load on piston.

A. 88000 n
B. 90560 n
C. 78036 n
D. 88357 n
Answer» D. 88357 n
21.

2 m and the cylinder bore is 0.5 m. engine runs at 250 r.p.m & 30° from T.D.C. Find the piston effort.

A. 32.4 kn
B. 35.2 kn
C. 37.3 kn
D. 40.2 n
Answer» C. 37.3 kn
22.

Multi cylinder engines are usually placed at an equal inclination to each other.

A. true
B. false
Answer» A. true
23.

For a multicylinder engine, the coefficient of fluctuation of speed would vary with

A. number of cylinders
B. remains unaffected
C. length of connecting rod
D. input temperature
Answer» B. remains unaffected
24.

For a 4 cylinder engine, if the minimum speed of the engine is half the maximum speed, then coefficient of fluctuation is

A. 0.5
B. 1.5
C. 2
D. 0.66
Answer» D. 0.66
25.

In the turning moment diagram of a multicylinder engine, the work done during exhaust stroke is by              

A. the gases
B. on the gases
C. piston wall
D. valve
Answer» B. on the gases
26.

For a 4 cylinder engine, when the pressure inside the cylinders exceeds the atmospheric pressure then.

A. work is done by the gases
B. work is done on the gases
C. work is done on the piston wall
D. work is done by the piston wall
Answer» A. work is done by the gases
27.

In a punching press, which of the following quantity is constant?

A. load
B. torque
C. angular velocity
D. angle of rotation
Answer» B. torque
28.

In a punching press, load is 0 at the time of punching.

A. true
B. false
Answer» B. false
29.

The maximum shear force required for punching depends on                  

A. sheared area
B. length of the plate
C. speed of the flywheel
D. total load
Answer» A. sheared area
30.

A machine punching 38 mm holes in 32 mm thick plate requires 7 N-m of energy per sq. mm of sheared area, find the maximum shear force required.

A. 26.7 kn
B. 53.4 kn
C. 13.35 kn
D. 106.8 kn
Answer» A. 26.7 kn
31.

The relation between stroke punch s and radius of crank r is              

A. s=r
B. s=2r
C. s=4r
D. s=r/2
Answer» B. s=2r
32.

If the stroke punch is 100mm, find the radius of the crank in mm.

A. 200
B. 100
C. 50
D. 400
Answer» C. 50
33.

Energy during actual punching operation is same as the energy supplied by the motor.

A. true
B. false
Answer» B. false
34.

The balance energy required for punching is supplied by the flywheel by                  

A. increase in its kinetic energy
B. decrease in its kinetic energy
C. decrease in its potential energy
D. by variation of mass
Answer» B. decrease in its kinetic energy
35.

When the length of the connecting rod is unknown then the value (θ2 –θ1)/2π is equal to                  

A. t/s
B. t/2s
C. t/2r
D. t/r
Answer» B. t/2s
36.

The size of a cam depends upon

A. base circle
B. pitch circle
C. prime circle
D. pitch curve
Answer» A. base circle
37.

The angle between the direction of the follower motion and a normal to the pitch curve is called

A. pitch angle
B. prime angle
C. base angle
D. pressure angle
Answer» D. pressure angle
38.

A circle drawn with centre as the cam centre and radius equal to the distance between the cam centre and the point on the pitch curve at which the pressure angle is maximum, is called

A. base circle
B. pitch circle
C. prime circle
D. none of the mentioned
Answer» B. pitch circle
39.

The cam follower generally used in automobile engines is

A. knife edge follower
B. flat faced follower
C. spherical faced follower
D. roller follower
Answer» C. spherical faced follower
40.

The cam follower extensively used in air- craft engines is

A. knife edge follower
B. flat faced follower
C. spherical faced follower
D. roller follower
Answer» D. roller follower
41.

In a radial cam, the follower moves

A. in a direction perpendicular to the cam axis
B. in a direction parallel to the cam axis
C. in any direction irrespective of the cam axis
D. along the cam axis
Answer» A. in a direction perpendicular to the cam axis
42.

A radial follower is one

A. that reciprocates in the guides
B. that oscillates
C. in which the follower translates along an axis passing through the cam centre of rotation.
D. none of the mentioned
Answer» A. that reciprocates in the guides
43.

Ofset is provided to a cam follower mechanism to

A. minimise the side thrust
B. accelerate
C. avoid jerk
D. none of the mentioned
Answer» A. minimise the side thrust
44.

For low and moderate speed engines, the cam follower should move with

A. uniform velocity
B. simple harmonic motion
C. uniform acceleration and retardation
D. cycloidal motion
Answer» B. simple harmonic motion
45.

For high speed engines, the cam follower should move with

A. uniform velocity
B. simple harmonic motion
C. uniform acceleration and retardation
D. cycloidal motion
Answer» D. cycloidal motion
46.

Which of the following displacement diagrams should be chosen for better dynamic performance of a cam-follower mechanism ?

A. simple hormonic motion
B. parabolic motion
C. cycloidal motion
D. none of the mentioned
Answer» C. cycloidal motion
47.

The linear velocity of the reciprocating roller follower when it has contact with the straight flanks of the tangent cam, is given by

A. ω(r1-r2)sinθ
B. ω(r1-r2)cosθ
C. ωr1+r2)sinθsec2θ
D. ω(r1+r2)cosθcosec2θ
Answer» C. ωr1+r2)sinθsec2θ
48.

The displacement of a flat faced follower when it has contact with the flank of a circular arc cam, is given by

A. r(1-cosθ)
B. r(1-sinθ)
C. (r-r1)(1-cosθ)
D. (r-r1)(1-sinθ)
Answer» C. (r-r1)(1-cosθ)
49.

The retardation of a flat faced follower when it has contact at the apex of the nose of a circular arc cam, is given by

A. ω2×oq
B. ω2×oqsinθ
C. ω2×oqcosθ
D. ω2×oqtanθ
Answer» A. ω2×oq
50.

Centre of masses of the system lies on the axis of rotation.

A. 1, 2, 3 and 4
B. 1, 2, and 3 only
C. 2, 3 and 4 only
D. 1, 3 and 4 only
Answer» D. 1, 3 and 4 only
51.

Which of the following statements is correct about the balancing of a mechanical system?

A. if it is under static balance, then there will be dynamic balance also
B. if it is under dynamic balance, then there will be static balance also
C. both static as well as dynamic balance have to be achieved separately
D. none of the mentioned
Answer» C. both static as well as dynamic balance have to be achieved separately
52.

In a locomotive, the ratio of the connecting rod length to the crank radius is kept very large in order to

A. minimize the effect of primary forces
B. minimize the effect of secondary forces
C. have perfect balancing
D. start the locomotive conveniently
Answer» B. minimize the effect of secondary forces
53.

In case of partial balancing of locomotives, the maximum magnitude of the unbalanced force perpendicular to the line of stroke is called hammer blow and this has to be limited by proper choice of the balancing mass and its radial position.

A. true
B. false
Answer» A. true
54.

Multi-cylinder engines are desirable because

A. only balancing problems are reduced
B. only flywheel size is reduced
C. both (a) and (b)
D. none of the mentioned
Answer» C. both (a) and (b)
55.

Secondary forces in reciprocating mass on engine frame are

A. of same frequency as of primary forces
B. twice the frequency as of primary forces
C. four times the frequency as of primary forces
D. none of the mentioned
Answer» B. twice the frequency as of primary forces
56.

Which of the following process is not the part of working of a 4 stroke I.C Engine?

A. compression
B. suction
C. exhaust
D. turbine flow
Answer» D. turbine flow
57.

4-stroke engine has one power stroke per 2 revolutions hence turning moment diagram is uniform.

A. true
B. false
Answer» B. false
58.

Work produced by the 4-stroke engine is less because                

A. one power stroke per 2 revolutions
B. one power stroke per revolution
C. one power stroke per 4 revolution
D. four power stroke per revolution
Answer» A. one power stroke per 2 revolutions
59.

A negative loop is formed in the turning moment diagram because the pressure inside the cylinder is                than the atmospheric pressure.

A. equal
B. more
C. less
D. no pressure inside
Answer» C. less
60.

When the work is by on the gases, which of the following effect is observed on the turning moment diagram?

A. formation of negative loop
B. formation of positive loop
C. formation of an infinite loop
D. formation of no loop
Answer» B. formation of positive loop
61.

Compression stroke results in                  

A. formation of negative loop
B. formation of positive loop
C. formation of an infinite loop
D. formation of no loop
Answer» A. formation of negative loop
62.

4 strokes engine have a lower thermal efficiency than 2 stroke engine.

A. true
B. false
Answer» B. false
63.

While drawing the turning moment diagram, which of the forces in not taken into account?

A. inertia force
B. force on connecting rod
C. force on crank
D. coriolis force
Answer» D. coriolis force
64.

In the given turning moment diagram, the process X is known as              

A. suction
B. compression
C. power
D. exhaust
Answer» C. power
65.

3 BALANCING MACHINES-FIELD BALANCING OF DISCS AND ROTORS.

A. centripetal forces
B. centrifugal forces
C. friction forces
D. inertia forces
Answer» D. inertia forces
66.

Balancing of single rotating mass by balancing masses in same plane and in different planes cannot take place.

A. true
B. false
Answer» B. false
67.

Which of the following is true for centrifugal force causing unbalance?

A. direction changes with rotation
B. magnitude changes with rotation
C. direction and magnitude both change with rotation
D. direction and magnitude both remain unchanged with rotation
Answer» A. direction changes with rotation
68.

In a revolving rotor, the centrifugal force remains balanced as long as the centre of the mass of the rotor lies                        

A. below the axis of shaft
B. on the axis of the shaft
C. above the axis of shaft
D. away from the axis of shaft
Answer» B. on the axis of the shaft
69.

If the unbalanced system is not set right then.

A. static forces develop
B. dynamic forces develop
C. tangential forces develop
D. radial forces develop
Answer» A. static forces develop
70.

What is not the effect of unbalanced forces?

A. load on bearings
B. dangerous vibrations
C. stresses in various members
D. violation of conservation of mass principle
Answer» D. violation of conservation of mass principle
71.

What is the effect of a rotating mass of a shaft on a system?

A. bend the shaft
B. twist the shaft
C. extend the shaft
D. compress the shaft
Answer» A. bend the shaft
72.

Balancing of reciprocating masses is the process of providing the second mass in order to counteract the effect of the centrifugal force of the first mass.

A. true
B. false
Answer» B. false
73.

The critical speed of a shaft with a disc supported in between is equal to the natural frequency of the system in

A. transverse vibrations
B. torsional vibrations
C. longitudinal vibrations
D. none of the mentioned
Answer» A. transverse vibrations
74.

When there is a reduction in amplitude over every cycle of vibration, then the body is said to have

A. free vibration
B. forced vibration
C. damped vibration
D. under damped vibration
Answer» C. damped vibration
75.

In vibration isolation system, if ω/ωn < 2, then for all values of damping factor, the transmissibility will be

A. less than unity
B. equal to unity
C. greater than unity
D. zero
Answer» C. greater than unity
76.

The accelerometer is used as a transducer to measure earthquake in Richter scale. Its design is based on the principle that

A. its natural frequency is very low in comparison to the frequency of vibration
B. its natural frequency is very high in comparison to the frequency of vibration
C. its natural frequency is equal to the frequency of vibration
D. measurement of vibratory motion is without any reference point
Answer» C. its natural frequency is equal to the frequency of vibration
77.

Critical speed is expressed as

A. rotation of shaft in degrees
B. rotation of shaft in radians
C. rotation of shaft in minutes
D. natural frequency of the shaft
Answer» D. natural frequency of the shaft
78.

The first critical speed of an automobile running on a sinusoidal road is calculated by (modeling it as a single degree of freedom system)

A. resonance
B. approximation
C. superposition
D. rayleigh quotient
Answer» A. resonance
79.

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» A. ωn
80.

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» A. 0.471 and 1.19 hz
81.

If the crank and the connecting rod are 300 mm and 1 m long respectively and the crank rotates at a constant speed of 250 r.p.m., determine the crank angle at which the maximum velocity occurs is          

A. 45
B. 75
C. 90
D. 60
Answer» B. 75
82.

5 m/s.

A. 4.19
B. 5
C. 3.49
D. 3.36
Answer» C. 3.49
83.

Which of the following expression represent the angular acceleration α of the connecting rod?

A. −ω2 . sin θ/n
B. −ω2 . cos θ.n
C. ω2. cos θ/n
D. ω2 . sin θ.n
Answer» A. −ω2 . sin θ/n
84.

While calculating angular acceleration of the connecting rod, sin2(θ) term is neglected.

A. true
B. false
Answer» A. true
85.

In a slider crank mechanism, the length of the crank and connecting rod are 180 mm and 540 mm respectively. The crank position is 45° from inner dead centre. The crank shaft speed is 450 r.p.m. (clockwise), calculate angular velocity of the connecting rod in rad/s.

A. 10.3
B. 11.1
C. 12.2
D. 11.8
Answer» B. 11.1
86.

When a body is subjected to transverse vibrations, the stress induced in a body will be

A. shear stress
B. bending stress
C. tensile stress
D. compressive stress
Answer» B. bending stress
87.

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» A. ωn
88.

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» C. occurs when excitation frequency is equal to undamped natural frequency
89.

When there is a reduction in amplitude over every cycle of vibration, then the body is said to have

A. free vibration
B. forced vibration
C. damped vibration
D. none of the mentioned
Answer» C. damped vibration
90.

Longitudinal vibrations are said to occur when the particles of a body moves

A. perpendicular to its axis
B. parallel to its axis
C. in a circle about its axis
D. none of the mentioned
Answer» B. parallel to its axis
91.

When a body is subjected to transverse vibrations, the stress induced in a body will be

A. shear stress
B. tensile stress
C. compressive stress
D. none of the mentioned
Answer» B. tensile stress
92.

The natural frequency (in Hz) of free longitudinal vibrations is equal to

A. 1/2π√s/m
B. 1/2π√g/δ
C. 0.4985/δ
D. all of the mentioned
Answer» D. all of the mentioned
93.

The factor which affects the critical speed of a shaft is

A. diameter of the disc
B. span of the shaft
C. eccentricity
D. all of the mentioned
Answer» D. all of the mentioned
94.

In under damped vibrating system, if x1 and x2 are the successive values of the amplitude on the same side of the mean position, then the logarithmic decrement is equal to

A. x1/x2
B. log (x1/x2)
C. loge (x1/x2)
D. log (x1.x2)
Answer» B. log (x1/x2)
95.

The ratio of the maximum displacement of the forced vibration to the deflection due to the static force, is known as

A. damping factor
B. damping coefficient
C. logarithmic decrement
D. magnification factor
Answer» D. magnification factor
96.

Which of the following systems produce a vibration in the foundation?

A. unbalanced machine
B. balanced machine
C. coupled machine
D. uncoupled machine
Answer» A. unbalanced machine
97.

When a periodic disturbing force is applied to a machine, the force is transmitted to the foundation by the means of spring.

A. true
B. false
Answer» A. true
98.

Which of the following is correct regarding isolation factor?

A. dimensionless quantity
B. has newton as its unit
C. has joule as its unit
D. has hz as its unit
Answer» A. dimensionless quantity
99.

Which of the following is a type of transmitted force to the foundation?

A. damping force
B. undamping force
C. tensile force
D. torsional force
Answer» A. damping force
100.

If isolation factor is negative, then what is the phase difference between transmitted and disturbing force?

A. 180°
B. 90°
C. 450°
D. 360°
Answer» A. 180°
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