1000+ Theory of Machines MCQ for RBI Grade B officer [Solved]

1. Higher pairs are those which have
A. Point or line contact between the two elements when in motion
B. Surface contact between the two elements when in motion
C. Elements of pairs not held together mechanically
D. Two elements that permit relative motion
Answer : A

2. 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
Answer : D

3. The size of cam depends upon
A. Base circle
B. Pitch circle
C. Prime circle
D. Pitch curve
Answer : A

4. When a shaking force is transmitted through the springs, damping becomes detrimental when the ratio of its frequency to the natural frequency is greater than
A. 0.25
B. 0.5
C. 1
D. 2
Answer : D

5. In a reciprocating engine, usually __________ of the reciprocating masses are balanced.
A. One-half
B. Two-third
C. Three-fourth
D. Whole
Answer : B

6. When the speed of the engine fluctuates continuously above and below the mean speed, the governor is said to be
A. Stable
B. Unstable
C. Isochronous
D. Hunt
Answer : D

7. 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
Answer : B

8. In order to facilitate starting of locomotive in any position, the cranks of a locomotive with two cylinders, are placed at
A. 45° to each other
B. 90° to each other
C. 120° to each other
D. 180° to each other
Answer : B

9. The example of completely constrained motion is a
A. Motion of a piston in the cylinder of a steam engine
B. Motion of a square bar in a square hole
C. Motion of a shaft with collars at each end in a circular hole
D. All of the above
Answer : D

10. The magnitude of velocities of the points on a rigid link is
A. Directly proportional to the distance from the points to the instantaneous centre and is parallel to the line joining the point to the instantaneous centre
B. Directly proportional to the distance from the points to the instantaneous centre and is perpendicular to the line joining the point to the instantaneous centre
C. Inversely proportional to the distance from the points to the instantaneous centre and is parallel to the line joining the point to the instantaneous centre
D. Inversely proportional to the distance from the points to the instantaneous centre and is perpendicular to the line joining the point to the instantaneous centre
Answer : D

11. The transmissibility, for all values of damping factor, will be less than unity, if ?/?_n is
A. Equal to 1
B. Less than 2
C. Equal to 2
D. Greater than 2
Answer : D

12. In a Hartnell governor, if a spring of greater stiffness is used, then the governor will be
A. Less sensitive
B. More sensitive
C. Unaffected of sensitivity
D. Isochronous
Answer : A

13. Rectilinear motion of piston is converted into rotary by
A. Cross head
B. Slider crank
C. Connecting rod
D. Gudgeon pin
Answer : B

14. Which type of gear train is used in clock mechanism to join hour hand and minute hand?
A. Simple gear train
B. Compound gear train
C. Reverted gear train
D. Epicyclic gear train
Answer : D

15. In a Hartnell governor, the lift of the sleeve is given by (where r? and r? = Max. and min. radii of rotation, x = Length of ball arm of the lever, and y = Length of sleeve arm of the lever)
A. (r? + r?) (y/x)
B. (r? + r?) (x/y)
C. (r? - r?) (y/x)
D. (r? - r?) (x/y)
Answer : C

16. In a screw jack, the effort required to lower the load W is given by
A. P = W tan(? - ?)
B. P = W tan(? + ?)
C. P = W tan(? - ?)
D. P = W cos(? + ?)
Answer : C

17. The number of links and instantaneous centers in a reciprocating engine mechanism are
A. 4, 4
B. 4, 5
C. 5, 4
D. 4, 6
Answer : D

18. The secondary unbalanced force is maximum __________ in one revolution of the crank.
A. Two times
B. Four times
C. Eight times
D. Sixteen times
Answer : B

19. An automobile steering gear is an example of
A. Sliding pair
B. Rolling pair
C. Lower pair
D. Higher pair
Answer : C

20. To obviate axial thrust, following gear drive is used
A. Double helical gears having opposite teeth
B. Double helical gears having identical teeth
C. Single helical gear in which one of the teeth of helix angle a is more
D. Mutter gears
Answer : A

21. In vibration isolation system, the transmissibility will be equal to unity, for all values of damping factor, if ?/?n is
A. Equal to 1
B. Equal to 2
C. Less than 2
D. Greater than 2
Answer : B

22. The Hooke's joint consists of:
A. Two forks
B. One fork
C. Three forks
D. Four forks
Answer : A

23. In a mechanism, usually one link is fixed. If the fixed link is changed in a kinematic chain, then relative motion of other links
A. Will remain same
B. Will change
C. Could change or remain unaltered depending on which link is fixed
D. Will not occur
Answer : A

24. The lower pairs are __________ pairs.
A. Self-closed
B. Force-closed
C. Friction closed
D. None of these
Answer : A

25. 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
Answer : C

26. A chain comprises of 5 links having 5 joints. Is it kinematic chain?
A. Yes
B. No
C. It is a marginal case
D. Data are insufficient to determine it
Answer : B

27. A body of weight W is required to move up the rough inclined plane whose angle of inclination with the horizontal is ?. The effort applied parallel to the plane is given by (where ? = tan ? = Coefficient of friction between the plane and the body)
A. P = W tan ?
B. P = W tan (? + ?)
C. P = W (sin ? + ? cos ?)
D. P = W (cos ? + ? sin ?)
Answer : C

28. The velocity of a body moving with simple harmonic motion is __________ at the mean position.
A. Zero
B. Minimum
C. Maximum
D. None of these
Answer : C

29. The method of obtaining different mechanisms by fixing in turn different links in a kinematic chain, is known as
A. Structure
B. Machine
C. Inversion
D. Compound mechanism
Answer : C

30. The unbalanced force due to reciprocating masses
A. Varies in magnitude but constant in direction
B. Varies in direction but constant in magnitude
C. Varies in magnitude and direction both
D. Constant in magnitude and direction both
Answer : A

31. The magnitude of linear velocity of a point B on a link AB relative to point A is (Where ? = Angular velocity of the link AB)
A. ? × AB
B. ? × (AB)²
C. ?² × AB
D. (? × AB)²
Answer : A

32. 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
Answer : B

33. A cam mechanism imparts following motion
A. Rotating
B. Oscillating
C. Reciprocating
D. All of the above
Answer : D

34. If the damping factor for a vibrating system is unity, then the system will be
A. Over damped
B. Under damped
C. Critically damped
D. Without vibrations
Answer : C

35. When the two elements of a pair have __________ when in motion, it is said to a lower pair.
A. Line or point contact
B. Surface contact
C. Body contact
D. None of these
Answer : B

36. The radius of a friction circle for a shaft rotating inside a bearing is (where r = Radius of shaft, and tan ? = Coefficient of friction between the shaft and bearing)
A. r sin?
B. r cos?
C. r tan?
D. (r/2) cos?
Answer : A

37. In a locomotive, the resultant unbalanced force due to the two cylinders along the line of stroke, is known as
A. Tractive force
B. Swaying couple
C. Hammer blow
D. None of these
Answer : A

38. ________ is an inversion of Double slider crank chain.
A. Coupling rod of a locomotive
B. Scotch yoke mechanism
C. Hand pump
D. Reciprocating engine
Answer : B

39. 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
Answer : B

40. The static balancing is satisfactory for low speed rotors but with increasing speeds, dynamic balancing becomes necessary. This is because, the
A. Unbalanced couples are caused only at higher speeds
B. Unbalanced forces are not dangerous at higher speeds
C. Effects of unbalances are proportional to the square of the speed
D. Effects of unbalances are directly proportional to the speed
Answer : C

41. For two governors A and B, the lift of sleeve of governor A is more than that of governor B, for a given fractional change in speed. It indicates that
A. Governor A is more sensitive than governor B
B. Governor B is more sensitive than governor A
C. Both governors A and B are equally sensitive
D. None of the above
Answer : A

42. The arrangement is called bevel gearing, when two __________ are connected by gears.
A Intersecting and coplanar shafts
B. Nonintersecting and non-coplanar shafts
C. Parallel and coplanar shafts
D. Parallel and non-coplanar shafts
Answer : A

43. In the two rotor system as shown in the below figure (I? < I?), a node of vibration is situated
A. Between I?, and I? but nearer I?
B. Between I?, and I? but nearer to I?
C. Exactly in the middle of the shaft
D. Nearer to I? but outside
Answer : B

44. In a mechanism, the fixed instantaneous centres are those centres which
A. Remain in the same place for all configurations of the mechanism
B. Vary with the configuration of the mechanism
C. Moves as the mechanism moves, but joints are of permanent nature
D. None of the above
Answer : A

45. The advantage of the piston valve over the slide valve is that in the former case
A. Wear is less
B. Power absorbed is less
C. Both wear and power absorbed are low
D. The pressure developed being high provides tight sealing
Answer : C

46. Typewriter constitutes
A. Machine
B. Structure
C. Mechanism
D. Inversion
Answer : C

47. The brake commonly used in railway trains is
A. Shoe brake
B. Band brake
C. Band and block brake
D. Internal expanding brake
Answer : A

48. In a multiple V-belt drive, if one of the belts is broken, then we should replace
A. The broken belt only
B. All the belts
C. The broken belt and the belts on either side of it
D. None of the above
Answer : B

49. A disc is a spinning with an angular velocity ? rad/s about the axis of spin. The couple applied to the disc causing precession will be (where I = Mass moment of inertia of the disc, and ?P = Angular velocity of precession of the axis of spin)
A. (1/2).I?²
B. I?²
C. (1/2). I ? ?_P
D. I ? ?_P
Answer : D

50. The mechanism in which two are turning pairs and two are sliding pairs, is called a
A. Double slider crank chain
B. Elliptical trammel
C. Scotch yoke mechanism
D. All of these
Answer : D