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

1. The equation of motion for a vibrating system with viscous damping is (d²x/dt²) + (c/m). (dx/dt) + (s/m). x = 0 If the roots of this equation are real, then the system will be
A. Over-damped
B. Under damped
C. Critically damped
D. Without vibrations
Answer : A

2. 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

3. 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

4. In a four-bar chain it is required to give an oscillatory motion to the follower for a continuous rotation of the crank. For the lengths of 50 mm of crank and 70 mm of the follower, determine theoretical maximum length of coupler. The distance between fixed pivots of crank and followers is
A. 95 mm
B. Slightly less than 95 mm
C. Slightly more than 95 mm
D. 45 mm
Answer : B

5. Shaft revolving in a bearing is the following type of pair
A. Lower pair
B. Higher pair
C. Spherical pair
D. Cylindrical pair
Answer : A

6. 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

7. The height of a Watt's governor is
A. Directly proportional to speed
B. Directly proportional to (speed)²
C. Inversely proportional to speed
D. Inversely proportional to (speed)²
Answer : D

8. In higher pair, the relative motion is
A. Purely turning
B. Purely sliding
C. Purely rotary
D. Combination of sliding and turning
Answer : D

9. 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

10. 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
Answer : C

11. Two systems shall be dynamically equivalent when
A. The mass of two are same
B. C.G. of two coincides
C. M.I. of two about an axis through e.g. is equal
D. All of the above
Answer : D

12. 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

13. The minimum force required to slide a body of weight W on a rough horizontal plane is
A. W sin?
B. W cos?
C. W tan?
D. W cosec?
Answer : A

14. 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

15. The instantaneous centre of a rigid thin disc rolling on a plane rigid surface is located at
A. The centre of the disc
B. The point of contact
C. An infinite distance on the plane surface
D. The point on the circumference situated vertically opposite to the contact point
Answer : B

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

17. Idler pulley is used
A. For changing the direction of motion of the belt
B. For applying tension
C. For increasing velocity ratio
D. All of the above
Answer : B

18. A torsional system with discs of moment of inertia I? and I? as shown in the below figure, is gear driven such that the ratio of speed of shaft B to shaft A is 'G'. Neglecting the inertia of gears, the equivalent inertia of disc on shaft B at the speed of shaft A is equal to
A. G.I?
B. G².I?
C. I?/G
D. I?/G²
Answer : B

19. A kinematic chain is known as a mechanism when
A. None of the links is fixed
B. One of the links is fixed
C. Two of the links are fixed
D. None of these
Answer : B

20. A disturbing mass m? attached to the rotating shaft may be balanced by a single mass m? attached in the same plane of rotation as that of m?, such that (where r? and r? are the radii of rotation of m? and m? respectively)
A. m?r? = m?r?
B. m?r? = m?r?
C. m?m? = r?r?
D. None of these
Answer : B

21. The coriolis component of acceleration is taken into account for
A. Slider crank mechanism
B. Four bar chain mechanism
C. Quick return motion mechanism
D. All of these
Answer : C

22. The unbalanced primary forces in a reciprocating engine are
A. Balanced completely
B. Balanced partially
C. Balanced by secondary forces
D. Not balanced
Answer : B

23. The number of links in pantograph mechanism is equal to
A. 2
B. 3
C. 4
D. 5
Answer : C

24. In gears, interference takes place when
A. The tip of a tooth of a mating gear digs into the portion between base and root circles
B. Gears do not move smoothly in the absence of lubrication
C. Pitch of the gears is not same
D. Gear teeth are undercut
Answer : A

25. The frequency of oscillation at compared to earth will be
A. 6 times more
B. 6 times less
C. 2.44 times more
D. 2.44 times less
Answer : D

26. The frequency of damped vibrations with viscous damping is ________ the frequency of undamped vibrations.
A. More than
B. Less than
C. Same as
D. None of these
Answer : B

27. The type of gears used to connect two non parallel and non intersecting shafts is
A. Spur gear
B. Helical gear
C. Bevel gear
D. Spiral gear
Answer : D

28. A body is said to be under forced vibrations, when
A. There is a reduction in amplitude after every cycle of vibration
B. No external force acts on a body, after giving it an initial displacement
C. A body vibrates under the influence of external force
D. None of the above
Answer : A

29. The length of a simple pendulum which gives the same frequency as the compound pendulum, is
A. k_G + l?
B. k_G² + l?
C. (k_G² + l?²)/ l?
D. (k_G + l?²)/ l?
Answer : C

30. When the nature of contact between the elements of a pair is such that it can only slide relative to the other, the pair is known as a
A. Screw pair
B. Spherical pair
C. Turning pair
D. Sliding pair
Answer : D

31. Torsional 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 these
Answer : C

32. The product of the diametral pitch and circular pitch is equal to
A. 1
B. 1/?
C. ?
D. 2 ?
Answer : C

33. Frequency of vibrations is usually expressed in
A. Number of cycles per hour
B. Number of cycles per minute
C. Number of cycles per second
D. None of these
Answer : C

34. The frequency of oscillation of a compound pendulum is
A. 2?. ?[gh/(k_G² + h²)]
B. 2?. ?[(k_G² + h²)/gh]
C. (1/2?). ?[gh/(k_G² + h²)]
D. (1/2?). ?[(k_G² + h²)/gh]
Answer : C

35. V-belts are usually used for
A. Long drives
B. Short drives
C. Long and short drives
D. None of these
Answer : B

36. Which of the following would constitute a link?
A. Piston, piston rod and cross head
B. Piston and piston rod
C. Piston rod and cross head
D. Piston, crank pin and crank shaft
Answer : A

37. Critical damping is a function of
A. Mass and stiffness
B. Mass and damping coefficient
C. Mass and natural frequency
D. Damping coefficient and natural frequency
Answer : A

38. 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 on the tight side and slack side of the belt
D. Average tension of the tight side and slack side of the belt
Answer : D

39. The size of a gear is usually specified by
A. Pressure angle
B. Circular pitch
C. Diametral pitch
D. Pitch circle diameter
Answer : D

40. The Klein's method of construction for reciprocating engine mechanism
A. Is based on acceleration diagram
B. Is a simplified form of instantaneous center method
C. Utilises a quadrilateral similar to the diagram of mechanism for reciprocating engine
D. Enables determination of Carioles component
Answer : C

41. Efficiency of a screw jack is given by
A. tan (? + ?)/tan?
B. tan?/tan (? +?)
C. tan (? - ?)/tan?
D. tan?/tan (? - ?)
Answer : B

42. Ball and a Socket forms a
A. Turning pair
B. Rolling pair
C. Screw pair
D. Spherical pair
Answer : D

44. The swaying couple is due to the
A. Primary unbalanced force
B. Secondary unbalanced force
C. Two cylinders of locomotive
D. Partial balancing
Answer : A

45. 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

46. 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

47. 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

48. A rotary internal combustion engine has __________ cylinders.
A. Four
B. Five
C. Six
D. Seven
Answer : D

49. If the opposite links of a four bar linkage are equal, the links will always form a
A. Triangle
B. Rectangle
C. Parallelogram
D. Pentagon
Answer : C

50. When the crank is at the inner dead centre, in a reciprocating steam engine, then the acceleration of the piston will be
A. ?²r. (n + 1)/n
B. ?²r. (n - 1)/n
C. ?²r. n/(n + 1)
D. ?²r. n/(n - 1)
Answer : A