# Theory of machines MCQ Questions & Answers

Theory of machines MCQs : This section focuses on the "Theory of machines". These Multiple Choice Questions (MCQs) should be practiced to improve the Theory of machines skills required for various interviews (campus interview, walk-in interview, company interview), placement, entrance exam and other competitive examinations.

Question 1

A disturbing mass m1 attached to the rotating shaft may be balanced by a single mass m2 attached in the same plane of rotation as that of m1, such that (where r1 and r2 are the radii of rotation of m1 and m2 respectively)

A. m1r2 = m2r1
B. m1r1 = m2r2
C. m1m2 = r1r2
D. none of these

Question 2

A mass of 1 kg is attached to the end of a spring with a stiffness of 0.7 N/mm. The critical damping coefficient of this system is

A. 1.4 N-s/m
B. 18.52 N-s/m
C. 52.92 N-s/m
D. 529.2 N-s/m

Question 3

A pair of friction discs is an example of rolling pair.

A. TRUE
B. FALSE

Question 4

A shaft has an attached disc at the centre of its length. The disc has its centre of gravity located at a distance of 2 mm from the axis of the shaft. When the shaft is allowed to vibrate in its natural bow-shaped mode, it has a frequency of vibration of 10 rad/s. When the shaft is rotated at 300 r.p.m., it will whirl with a radius of

A. 2 mm
B. 2.22 mm
C. 2.50 mm
D. 3.0 mm

Question 5

An automobile steering gear is an example of

A. sliding pair
B. rolling pair
C. lower pair
D. higher pair

Question 6

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

Question 7

If ω/ωn = 2, where co is the frequency of excitation and ωn is the natural frequency of vibrations, then the transmissibility of vibration will the

A. 0.5
B. 1
C. 1.5
D. 2

Question 8

If ω/ωn is very high for a body vibrating under steady state vibrations, the phase angle for all values of damping factors, will tend to approach

A. 0°
B. 90°
C. 180°
D. 360°

Question 9

In a circular arc cam with roller follower, the acceleration in any position of the lift will depend only upon

A. total lift, total angle of lift, minimum radius of cam and cam speed
B. radius of circular arc, cam speed, location of centre of circular arc and roller diameter
C. mass of cam follower linkage, spring stiffness and cam speed
D. total lift, centre of gravity of the cam and cam speed

Question 10

In a coupling rod of a locomotive, each of the four pairs is a __________ pair.

A. sliding
B. turning
C. rolling
D. screw

Question 11

In a screw jack, the effort required to lower the load W is given by

A. P = W tan(α - φ)
B. P = W tan(α + φ)
C. P = W tan(φ - α)
D. P = W cos(α + φ)

Question 12

In a vibrating system, if the actual damping coefficient is 40 N/m/s and critical damping coefficient is 420 N/m/s, then logarithmic decrement is equal to

A. 0.2
B. 0.4
C. 0.6
D. 0.8

Question 13

In order to balance the reciprocating masses,

A. primary forces and couples must be balanced
B. secondary forces and couples must be balanced
C. both (a) and (b)
D. none of these

Question 14

In order to give the primary balance of the reciprocating parts of a multi-cylinder in-line engines,

A. the algebraic sum of the primary forces must be equal to zero
B. the algebraic sum of the couples about any point in the plane of the primary forces must be equal to zero
C. both (a) and (b)
D. none of these

Question 15

In railway axle boxes, the bearing used is

A. deep groove ball bearing
B. double row self-aligning ball bearing
C. double row spherical roller bearing
D. cylindrical roller bearing

Question 16

In under damped vibrating system, the amplitude of vibration

A. decreases linearly with time
B. increases linearly with time
C. decreases exponentially with time
D. increases exponentially with time

Question 17

In vibration isolation system, the transmissibility will be equal to unity, for all values of damping factor, if ω/ωn is

A. equal to one
B. equal to 2
C. less than 2
D. greater than 2

Question 18

The acceleration of the particle moving with simple harmonic motion is inversely proportional to the displacement of the particle from the mean position.

A. Yes
B. No

Question 19

The cam follower generally used in automobile engines is

A. knife edge follower
B. fiat faced follower
C. spherical faced follower
D. roller follower

Question 20

The dynamic friction is the friction experienced by a body, when the body

A. is in motion
B. is at rest
C. just begins to slide over the surface of the other body
D. none of the above

Question 21

The factor which affects the critical speed of a shaft is

A. diameter of disc
B. span of shaft
C. eccentricity
D. all of these

Question 22

The frequency of damped vibrations with viscous damping is __________ the frequency of undamped vibrations.

A. more than
B. less than
C. same as

Question 23

The frictional torque transmitted in a multi-collared shaft is same as that of a single collared shaft.

A. Right
B. Wrong

Question 24

The gear train usually employed in clocks is a

A. simple gear train
B. reverted gear train
C. sun and planet gear
D. differential gear

Question 25

The gears are termed as medium velocity gears, if their peripheral velocity is

A. 1 - 3 m/s
B. 3 - 15 m/s
C. 15 - 30 m/s
D. 30 - 50 m/s

Question 26

The pair is known as a higher pair, when the relative motion between the elements of a pair is

A. turning only
B. sliding only
C. rolling only
D. partly turning and partly sliding

Question 27

The partial balancing of reciprocating parts in locomotives produces

A. hammer blow
B. swaying couple
C. variation in tractive force along the line of stroke
D. all of the above

Question 28

The pressure angle of a cam is the angle between the direction of the follower motion and a normal to the

A. pitch circle
B. base circle
C. pitch curve
D. prime circle

Question 29

The primary unbalanced force is maximum when the angle of inclination of the crank with the line of stroke is

A. 0° and 90°
B. 0° and 180°
C. 90° and 180°
D. 180° and 360°

Question 30

The radial distance of a tooth from the pitch circle to the bottom of the tooth is called

A. dedendum
C. clearance
D. working depth

Question 31

The ratio of the actual damping coefficient to the critical damping coefficient is called damping factor.

A. Yes
B. No

Question 32

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. Agree
B. Disagree

Question 33

The sliding pairs, turning pairs and screw pairs form lower pairs.

A. TRUE
B. FALSE

Question 34

The static friction

A. bears a constant ratio to the normal reaction between the two surfaces
B. is independent of the area of contact, between the two surfaces
C. always acts in a direction, opposite to that in which the body tends to move
D. all of the above

Question 35

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 above

Question 36

The swaying couple is maximum or minimum when the angle of inclination of the crank to the line of stroke (θ) is equal to

A. 90° and 180°
B. 45° and 225°
C. 180° and 270°
D. 270° and 360°

Question 37

The tractive force in a locomotive with two cylinders is given by (where c = Fraction of reciprocating parts per cylinder, m = Mass of reciprocating parts, ω = Angular speed of crank, r = Radius of crank, and θ = Angle of inclination of crank to the line of stroke)

A. m.ω2.r cos θ
B. c.m.ω2.r sin θ
C. (1 - c)m.ω2.r(cos θ - sin θ)
D. m.ω2.r(cos θ - sin θ)

Question 38

The two elements of a pair are said to form a __________ when they permit relative motion between them.

A. open pair
B. kinematic pair

Question 39

The two links OA and OB are connected by a pin joint at O. If the link OA turns with angular velocity ω1 rad/s in the clockwise direction and the link OB turns with angular velocity ω2 rad/s in the clockwise direction, then the rubbing velocity at the pin joint O is (where r = Radius of the pin at O)

A. ω1.ω2.r
B. ( ω1 - ω2)r
C. ( ω1 + ω2)r
D. ( ω1 - ω2)2r

Question 40

The Whitworth quick return motion mechanism is formed in a slider crank chain when the

C. slider is a fixed link

Question 41

When a body moves with simple harmonic motion, the product of its periodic time and frequency is equal to

A. zero
B. one
C. π/2
D. π

Question 42

When a particle moves round the circumference of a circle of radius r with ω rad/s, then its maximum acceleration is ω2r.

A. Right
B. Wrong

Question 43

When the axes of the shafts, over which the gears are mounted, move relative to a fixed axis, then the train is known as reverted gear train.

A. Right
B. Wrong

Question 44

When the connection between the two elements is such that only required kind of relative motion occurs, it is known as self-closed pair.

A. Right
B. Wrong

Question 45

When the crank is at the inner dead centre, in a reciprocating steam engine, then the velocity of the piston will be

A. minimum
B. zero
C. maximum
D. none of these

Question 46

When the relation between the controlling force (Fc) and radius of rotation (r) for a spring controlled governor is Fc = ar + b, then the governor will be

A. stable
B. unstable
C. isochronous
D. none of these

Question 47

When the two elements of a pair have a surface contact when relative motion takes place and the surface of one element slides over the surface of the other, the pair formed is known as a

A. lower pair
B. higher pair
C. self-closed pair
D. force-closed pair