RRB Group D - Theory of Machines 1000+ MCQ [Solved] PDF Download

1. When one of the links of a kinematic chain is fixed, the chain is known as a
A. Structure
B. Mechanism
C. Inversion
D. Machine
Answer : B

2. The displacement of the reciprocating roller follower, when it has contact with the straight flanks of the tangent cam, is given by (where r? = Minimum radius of the cam, r? = Radius of the roller follower, and ? = Angle turned by the cam from the beginning of the follower displacement)
A. (r? - r?) (1 - cos?)
B. (r? + r?) (1 + cos?)
C. (r? - r?) [(1 - cos?)/cos ?]
D. (r? + r?) [(1 - cos?)/cos ?]
Answer : D

3. The minimum number of teeth on the pinion which will mesh with any gear without interference for 20° full depth involute teeth will be
A. 12
B. 14
C. 18
D. 24
Answer : C

4. If the pressure angle is __________, a reciprocating follower will jam in its bearings.
A. Small
B. Too small
C. Large
D. Too large
Answer : D

5. Two pulleys of radii r? and r? and at distance x apart are connected by means of a cross belt drive. The length of the belt is
A. ? (r? + r?) + [(r? + r?)²/x] + 2x
B. ? (r? + r?) + [(r? - r?)²/x] + 2x
C. ? (r? - r?) + [(r? - r?)²/x] + 2x
D. ? (r? - r?) + [(r? + r?)²/x] + 2x
Answer : A

6. 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
Answer : A

7. A system in dynamic balance implies that
A. The system is critically damped
B. There is no critical speed in the system
C. The system is also statically balanced
D. There will absolutely no wear of bearings
Answer : C

8. In a steam engine, the link constitutes a
A. Piston, piston rod and crosshead
B. Connecting rod with big and small end brasses, caps and bolts
C. Crank pin, crankshaft and flywheel
D. All of the above
Answer : D

9. In the below figure, PC is the connecting rod and OC is the crank making an angle ? with the line of stroke PO and rotates with uniform angular velocity at ? rad/s. The Klien's acceleration diagram for determining the acceleration of the piston P is shown by quadrilateral CQNO. The acceleration of the piston P with respect to the crankpin C is given by
A. ?² × NO
B. ?² × CO
C. ?² × CN
D. ?² × QN
Answer : C

10. 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 sideways
D. None of the above
Answer : B

11. The included angle for the V-belt is usually
A. 10° to 20°
B. 20° to 30°
C. 30° to 40°
D. 60° to 80°
Answer : C

12. In a reciprocating steam engine, when the crank has turned from inner dead centre through an angle ?, the angular velocity of the connecting rod is given by
A. ? sin?/(n² - sin²?)^1/2
B. ? cos?/(n² - cos²?)^1/2
C. ? sin?/(n² - cos²?)^1/2
D. ? cos?/(n² - sin²?)^1/2
Answer : D

13. 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

14. 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

15. The motion between a pair which takes place in __________ is known as incompletely constrained motion.
A. One direction only
B. Two directions only
C. More than one direction
D. None of these
Answer : C

16. When the nature of contact between the elements of a pair is such that one element can turn about the other by screw threads, the pair is known as a
A. Screw pair
B. Spherical pair
C. Turning pair
D. Sliding pair
Answer : A

17. The acceleration of a flat-faced follower when it has contact with the flank of a circular arc cam, is given by
A. ?² R cos?
B. ?² (R - r?) cos?
C. ?² (R - r?) sin?
D. ?² r? sin?
Answer : B

18. Module of a gear is
A. D/T
B. T/D
C. 2D/T
D. 2T/D
Answer : A

19. 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
Answer : A

20. Balancing of rotating and reciprocating parts of an engine is necessary when it runs at
A. Slow speed
B. Moderate speed
C. Highs peed
D. Any one of these
Answer : C

21. Which of the following governor is used to drive a gramophone?
A. Watt governor
B. Porter governor
C. Pickering governor
D. Hartnell governor
Answer : C

22. The power from the engine to the rear axle of an automobile is transmitted by means of
A. Worm and worm wheel
B. Spur gears
C. Bevel gears
D. Hooke's joint
Answer : D

23. In a multiple V-belt drive, when a single belt is damaged, it is preferable to change the complete set to
A. Reduce vibration
B. Reduce slip
C. Ensure uniform loading
D. Ensure proper alignment
Answer : C

24. 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

25. ABCD is a four bar mechanism in which AB = 310 mm and CD = 450 mm. AB and CD are both perpendicular to the fixed link AD, as shown in the below figure. If the velocity of B at this condition is v. Then the velocity of C is
A. v
B. (2/3). v
C. (3/2). v
D. (9/4). v
Answer : C

26. A body in motion will be subjected to coriolis acceleration when that body is
A. In plane rotation with variable velocity
B. In plane translation with variable velocity
C. In plane motion which is a resultant of plane translation and rotation
D. Restrained to rotate while sliding over another body
Answer : D

27. In a Hartnell governor, the stiffness of the spring is given by (where S1 and S2 = Spring forces exerted on the sleeve at max. and min. radii of rotation, and h = Compression of the spring)
A. (S? + S?)/h
B. (S? - S?)/h
C. (S? + S?)/2h
D. (S? - S?)/2h
Answer : B

28. 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

29. In Meyer's expansion valve, the expansion valve is driven by an eccentric having an angle of advance from
A. 50°-60°
B. 60°-70°
C. 70°-80°
D. 80°-90°
Answer : D

30. The frictional torque transmitted in a flat collar bearing, considering uniform wear, is (where r? and r? = External and internal radii of collar respectively)
A. (1/2) ? W (r? + r?)
B. (2/3) ? W (r? + r?)
C. (1/2) ? W [(r?³ - r?³)/(r?² - r?²)]
D. (2/3) ? W [(r?³ - r?³)/(r?² - r?²)]
Answer : A

31. A mechanism consisting of four links is called a __________ mechanism.
A. Simple
B. Compound
C. Binary
D. None of these
Answer : A

32. 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

33. In a cam drive with uniform velocity follower, the sharp corners of the displacement diagram are rounded off at the beginning and at the end of each stroke. This is done
A. Because of difficulty in manufacturing cam profile
B. Because of loose contact of follower with cam surface
C. In order to have acceleration in beginning and retardation at the end of stroke within the finite limits
D. Because the uniform velocity motion is a partial parabolic motion
Answer : C

34. A pantograph is a mechanism with
A. Lower pairs
B. Higher pairs
C. Rolling pairs
D. Turning pairs
Answer : A

35. 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 energy
D. None of these
Answer : C

36. The absolute acceleration of any point P in a link about center of rotation O is
A. Along PO
B. Perpendicular to PO
C. At 45° to PO
D. None of the above
Answer : D

37. Which of the following is used to control the speed variations of the engine caused by the fluctuations of the engine turning moment?
A. D-slide valve
B. Governor
C. Flywheel
D. Meyer's expansion valve
Answer : C

38. Which of the following statement is correct?
A. The primary unbalanced force is less than the secondary unbalanced force.
B. The primary unbalanced force is maximum twice in one revolution of the crank.
C. The unbalanced force due to reciprocating masses varies in magnitude and direction boh.
D. The magnitude of swaying couple in locomotives is inversely proportional to the distance between the two cylinder centre lines
Answer : B

39. If ?/?n is very low 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°
Answer : A

40. A slider crank chain consists of following numbers of turning and sliding pairs
A. 1, 3
B. 2, 2
C. 3, 1
D. 4, 0
Answer : C

41. The Ackerman steering gear mechanism is preferred to the Davis steering gear mechanism, because
A. Whole of the mechanism in the Ackerman steering gear is on the back of the front wheels
B. The Ackerman steering gear consists of turning pairs
C. The Ackerman steering gear is most economical
D. Both (A) and (B)
Answer : D

42. The total number of instantaneous centres for a mechanism consisting of n links are
A. n/2
B. n
C. n - 1
D. n(n - 1)/2
Answer : D

43. When the load on the engine increases, it becomes necessary to increase the supply of working fluid and when the load decreases, less working fluid is required. The supply of the working fluid to the engine is controlled by a
A. D-slide valve
B. Governor
C. Meyer's expansion valve
D. Flywheel
Answer : B

44. When a slider moves on a fixed link having curved surface, their instantaneous centre lies
A. On their point of contact
B. At the centre of curvature
C. At the centre of circle
D. At the pin joint
Answer : B

45. The instantaneous centres which vary with the configuration of mechanism are called
A. Permanent instantaneous centres
B. Fixed instantaneous centres
C. Neither fixed nor permanent instantaneous centres
D. None of the above
Answer : C

46. 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. 2 W C_E / C_S
B. W C_E / 2C_S
C. W C_E / C_S
D. W C_S / 2C_E
Answer : B

47. The contact ratio is the ratio of
A. Length of pair of contact to the circular pitch
B. Length of arc of contact to the circular pitch
C. Length of arc of approach to the circular pitch
D. Length of arc of recess to the circular pitch
Answer : B

48. Which of the following is an open pair?
A. Journal bearing
B. Ball and Socket joint
C. Leave screw and nut
D. None of the above
Answer : C

49. The type of pair formed by two elements which are so connected that one is constrained to turn or revolve about a fixed axis of another element is known as
A. Turning pair
B. Rolling pair
C. Sliding pair
D. Spherical pair
Answer : A

50. The relation between number of links (l) and number of joints (j) in a kinematic chain is
A. l = (1/2).(j + 2)
B. l = (2/3).(j + 2)
C. l = (3/4).(j + 3)
D. l = j + 4
Answer : B