1000+ Theory of Machines MCQ for SSC JHT [Solved]

1. For dynamic balancing of a shaft
A. The net dynamic force acting on the shaft is equal to zero
B. The net couple due to the dynamic forces acting on the shaft is equal to zero
C. Both (A) and (B)
D. None of the above
Answer : C

2. The stress induced in a body will be shear stress, when it is subjected to
A. Longitudinal vibrations
B. Transverse vibrations
C. Torsional vibrations
D. None of these
Answer : C

3. The Scott-Russell mechanism consists of
A. Sliding and turning pairs
B. Sliding and rotary pairs
C. Turning and rotary pairs
D. Sliding pairs only
Answer : A

4. Two heavy rotating masses are connected by shafts of lengths l?, l? and l? and the corresponding diameters are d?, d? and d?. This system is reduced to a torsionally equivalent system having uniform diameter d = d? of the shaft. The equivalent length of the shaft is
A. (l? + l? + l?)/3
B. l = l? + l?.(d?/d?)³ + l?.(d?/d?)³
C. l = l? + l?.(d?/d?)? + l?.(d?/d?)?
D. l? + l? + l?
Answer : C

5. Open 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 : C

6. The coefficient of fluctuation of speed is __________ of maximum fluctuation of speed and the mean speed.
A. Sum
B. Difference
C. Product
D. Ratio
Answer : D

7. The critical speed of a shaft in revolution per second is __________ as that of natural frequency of transverse vibration.
A. Same
B. Different
C. Unpredictable
D. None of these
Answer : A

8. Cam angle is defined as the angle
A. During which the follower returns to its initial position
B. Of rotation of the cam for a definite displacement of the follower
C. Through which, the cam rotates during the period in which the follower remains in the highest position
D. Moved by the cam from the instant the follower begins to rise, till it reaches its highest position
Answer : B

9. For the brake to be self locking, the force P at C shown in the below figure, should
A. Be zero
B. Act in upward direction
C. Act in downward direction
D. None of these
Answer : A

10. The flank of the tooth is the surface of the tooth __________ the pitch surface.
A. Above
B. Below
C. At
D. None of these
Answer : B

11. Which of the following is false statement in respect of differences between machine and structure?
A. Machines transmit mechanical work, whereas structures transmit forces
B. In machines, relative motion exists between its members, whereas same does not exist in case of structures
C. Machines modify movement and work, whereas structures modify forces
D. Efficiency of machines as well as structures is below 100%
Answer : D

12. Transmission angle is the angle between
A. Input link and coupler
B. Input link and fixed link
C. Output link and coupler
D. Output link and fixed link
Answer : C

13. A point on a connecting link (excluding end points) of a double slider crank mechanism traces a
A. Straight line path
B. Hyperbolic path
C. Parabolic path
D. Elliptical path
Answer : D

14. In an open pair, the two elements of a pair
A. Have a surface contact when in motion
B. Have a line or point contact when in motion
C. Are kept in contact by the action of external forces, when in motion
D. Are not held together mechanically
Answer : D

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

16. 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

17. 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

18. 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

19. Klein's construction is useful to determine
A. Velocity of various parts
B. Acceleration of various parts
C. Displacement of various parts
D. Angular acceleration of various parts
Answer : B

20. Which one of the following can completely balance several masses revolving in different planes on a shaft?
A. A single mass in different planes
B. Two masses in any two planes
C. A single mass in one of the planes of the revolving masses
D. Two equal masses in any two planes
Answer : B

21. 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

22. The periodic time of one oscillation for a simple pendulum is
A. 2?. ?(g/l)
B. (1/2?). ?(g/l)
C. 2?. ?(l/g)
D. (1/2?). ?(l/g)
Answer : C

23. When a body moves with simple harmonic motion, the product of its periodic time and frequency is equal to
A. Zero
B. One
C. ?/2
D. ?
Answer : B

24. When the axes of the first and last wheels are coaxial, then the train is known as
A. Simple train of wheels
B. Compound train of wheels
C. Reverted gear train
D. Epicyclic gear train
Answer : C

25. Angle of dwell of cam is defined as the angle
A. During which the follower returns to its initial position
B. Of rotation of the cam for definite displacement of the follower
C. Through which the cam rotates during the period in which the follower remains in the highest position
D. Moved by the cam from the instant the follower begins to rise, till it reaches its highest position
Answer : C

26. 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

27. In a rigid link OA, velocity of A w.r.t. O will be
A. Parallel to OA
B. Perpendicular to OA
C. At 45° to OA
D. Along AO
Answer : B

28. A fixed gear having 200 teeth is in mesh with another gear having 50 teeth. The two gears are connected by an arm. The number of turns made by the smaller gear for one revolution of arm about the centre of bigger gear is
A. 2
B. 4
C. 3
D. None of the above
Answer : B

29. 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

30. Which of the following is an inversion of a double slider crank chain?
A. Oldham's coupling
B. Elliptical trammel
C. Scotch yoke mechanism
D. All of these
Answer : D

31. Which of the following disciplines provides study of the relative motion between the parts of a machine and the forces acting on the parts?
A. Theory of machines
B. Applied mechanics
C. Mechanisms
D. Kinetics
Answer : A

32. A friction circle is a circle drawn when a journal rotates in a bearing. Its radius depends upon the coefficient of friction and the
A. Magnitude of the forces on journal
B. Angular velocity of journal
C. Clearance between journal and bearing
D. Radius of journal
Answer : D

33. When the body is suspended at the point of suspension, its periodic time and frequency will be ________ as compared to the body suspended at the point of percussion.
A. Same
B. Two times
C. Four times
D. None of these
Answer : A

34. The angle of inclination of the plane, at which the body begins to move down the plane is called
A. Angle of friction
B. Angle of repose
C. Angle of projection
D. None of these
Answer : B

35. 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

36. A reed type tachometer use the principle of
A. Longitudinal vibration
B. Torsional vibration
C. Transverse vibration
D. Damped free vibration
Answer : C

37. The essential condition of placing the two masses, so that the system becomes dynamically equivalent, is (where l? and l? = Distance of two masses from the centre of gravity of the body, and kG = Radius of gyration of the body)
A. l? = k_G
B. l? = k_G
C. l?l? = k_G
D. l?l? = k_G²
Answer : D

38. When the elements of a pair are kept in contact by the action of external forces, the pair is said to be a
A. Lower pair
B. Higher pair
C. Self-closed pair
D. Force-closed pair
Answer : D

39. 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

40. For an involute gear, the rati of base circle radius and pitch circle radius is equal to
A. sin?
B. cos?
C. sec?
D. cosec?
Answer : B

41. The working depth of a gear is the radial distance from the
A. Pitch circle to the bottom of a tooth
B. Pitch circle to the top of a tooth
C. Top of a tooth to the bottom of a tooth
D. Addendum circle to the clearance circle
Answer : D

42. 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

43. Oldhams coupling is an inversion of the kinematic chain used in
A. Whitworth quick return mechanism
B. Elliptical trammels
C. Rotary engine
D. Universal joint
Answer : B

44. 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, if N coincides with O, then
A. Acceleration and velocity of the piston P is zero
B. Acceleration and velocity of the piston P is maximum
C. Acceleration of the piston P is zero and its velocity is maximum
D. Acceleration of the piston P is maximum and its velocity is zero
Answer : C

45. The natural frequency of free transverse vibrations due to a point load acting over a simply supported shaft is equal to (where ? = Static deflection of a simply supported shaft due to the point load)
A. 0.4985/??
B. 0.5615/??
C. 0.571/??
D. 0.6253/??
Answer : A

46. The train value of a gear train is
A. Equal to velocity ratio of a gear train
B. Reciprocal of velocity ratio of a gear train
C. Always greater than unity
D. Always less than unity
Answer : B

47. In elliptical trammels
A. All four pairs are turning
B. Three pairs turning and one pair sliding
C. Two pairs turning and two pairs sliding
D. One pair turning and three pairs sliding
Answer : C

48. Two pulleys of radii r? and r? and at distance x apart are connected by means of an open 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 : B

49. The type of coupling used to join two shafts whose axes are neither in same straight line nor parallel, but intersect is
A. Flexible coupling
B. Universal coupling
C. Chain coupling
D. Oldham's coupling
Answer : B

50. In locomotives, the ratio of the connecting rod length to me crank radius is kept very large in order to
A. Minimise the effect of primary forces
B. Minimise the effect of secondary forces
C. Have perfect balancing
D. To start the locomotive quickly
Answer : B