Theory of Machines MCQ Solved Paper for SSC Scientific Assistant

1. A circular bar moving in a round hole is an example of
A. Incompletely constrained motion
B. Partially constrained motion
C. Completely constrained motion
D. Successfully constrained motion
Answer : A

2. The relative velocity of B with respect to A in a rigid link AB is
A. Parallel to AB
B. Perpendicular to AB
C. Along AB
D. At 45° to AB
Answer : B

3. The critical speed of a shaft depends upon its
A. Mass
B. Stiffness
C. Mass and stiffness
D. Stiffness and eccentricity
Answer : C

4. 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

5. Pitch point on a cam is
A. Any point on pitch curve
B. The point on cam pitch curve having the maximum pressure angle
C. Any point on pitch circle
D. The point on cam pitch curve having the minimum pressure angle
Answer : B

6. Kinematic 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 : D

7. A shaft carrying two rotors at its ends will have
A. No node
B. One node
C. Two nodes
D. Three nodes
Answer : B

8. The periodic time is given by (where ? = Angular velocity of the particle in rad/s)
A. ?/2?
B. 2?/?
C. ? × 2?
D. ?/?
Answer : B

9. 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

10. A point B on a rigid link AB moves with respect to A with angular velocity ? rad/s. The radial component of the acceleration of B with respect to A, is (where vBA = Linear velocity of B with respect to A)
A. v_BA × AB
B. v_BA /AB
C. v²_BA
D. v²_BA /AB
Answer : D

11. The sensitiveness of the governor __________ as the speed range decreases.
A. Remains unaffected
B. Decreases
C. Increases
D. None of these
Answer : C

12. A rigid body possesses ________degrees of freedom
A. One
B. Two
C. Four
D. Six
Answer : D

13. 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 is _________ when the crank OC and connecting rod PC are at right angles to each other.
A. Infinity
B. Zero
C. Any +ve value
D. Any -ve value
Answer : B

14. For an isochronous Hartnell governor (where r? and r? = Maximum and minimum radius of rotation of balls respectively, S? and S? = Maximum and minimum force exerted on the sleeve respectively, and M = Mass on the sleeve)
A. (m.g + S?)/(m.g + S?) = r?/r?
B. (m.g - S?)/(m.g - S?) = r?/r?
C. S?/S? = r?/r?
D. S?/S? = r?/r?
Answer : A

15. The driving and driven shafts connected by a Hooke's joint will have equal speeds, if
A. cos? = sin?
B. sin? = ± tan?
C. tan? = ± cos?
D. cot? = cos?
Answer : C

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

17. The velocity of the rubbing surface __________ with the distance from the axis of the bearing.
A. Increases
B. Decreases
C. Remain same
D. None of these
Answer : A

18. In a flat collar pivot bearing, the moment due to friction is proportional to
A. (r?² - r?²)/(r? - r?)
B. (r?² - r?²)/(r? + r?)
C. (r?³ - r?³)/(r?² - r?²)
D. (r?³ - r?³)/(r? - r?)
Answer : C

19. 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

20. Scotch yoke mechanism is used to generate
A. Sine functions
B. Square roots
C. Logarithms
D. Inversions
Answer : A

21. A typewriter mechanism has 7 numbers of binary joints, six links and none of higher pairs. The mechanism is
A. Kinematically sound
B. Not sound
C. Soundness would depend upon which link is kept fixed
D. Data is not sufficient to determine same
Answer : A

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

23. Governor is used in automobile to
A. Decrease the variation of speed
B. Maximize the fuel economy
C. Limit the vehicle speed
D. Maintain constant engine speed
Answer : C

24. The ratio of the maximum displacement of the forced vibration to the deflection due to the static force, is known as
A. Damping factor
B. Damping coefficient
C. Logarithmic decrement
D. Magnification factor
Answer : D

25. The danger of breakage and vibration is maximum
A. Below the critical speed
B. Near the critical speed
C. Above the critical speed
D. None of these
Answer : B

26. The purpose of a link is to
A. Transmit motion
B. Guide other links
C. Act as a support
D. All of the above
Answer : D

27. 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. 3
C. 4
D. 5
Answer : C

28. 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

29. The maximum value of the pressure angle in case of cam is kept as
A. 10°
B. 14°
C. 20°
D. 30°
Answer : D

30. Davis steering gear consists of
A. Sliding pairs
B. Turning pairs
C. Rolling pairs
D. Higher pairs
Answer : A

31. The frictional torque transmitted in a flat pivot bearing, assuming uniform wear, is (Where ? = Coefficient of friction, W=Load over the bearing, R=Radius of bearing)
A. ?wr
B. ¾?WR
C. (2/3) ?WR
D. ½?WR
Answer : D

32. 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

33. Cylindrical cams can be classified as
A. Circular
B. Tangent
C. Reciprocating
D. None of the above
Answer : D

34. The velocity of sliding of meshing gear teeth is (Where ?? and ?? are angular velocities of meshing gears and y is distance between point of contact and the pitch point)
A. (?? + ??)y
B. (??/??)y
C. (?? × ??)y
D. (?? + ??)/y
Answer : C

35. Which of the following has sliding motion?
A. Crank
B. Connecting rod
C. Crank pin
D. Crosshead
Answer : D

36. The example of successfully constrained motion is a
A. Motion of an I.C. engine valve
B. Motion of the shaft between a footstep bearing
C. Piston reciprocating inside an engine cylinder
D. All of the above
Answer : D

37. 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

38. A system of masses rotating in different parallel planes is in dynamic balance if the
A. Resultant force is equal to zero
B. Resultant couple is equal to zero
C. Resultant force and resultant couple are both equal to zero
D. Resultant force is numerically equal to the resultant couple, but neither of them need necessarily be zero
Answer : C

39. 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

40. Effort of a governor is the
A. Mean force exerted at the sleeve for a given percentage change of speed
B. Workdone at the sleeve for maximum equilibrium speed
C. Mean force exerted at the sleeve for maximum equilibrium speed
D. None of the above
Answer : A

41. In its simplest form, a cam mechanism consists of following number of links
A. 1
B. 2
C. 3
D. 4
Answer : C

42. 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
Answer : C

44. 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

45. A spring controlled governor is said to be stable if the controlling force line when produced intersects the Y-axis
A. At the origin
B. Below the origin
C. Above the origin
D. Any one of these
Answer : B

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

47. 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
Answer : C

48. The radial distance from the top of a tooth to the bottom of a tooth in a meshing gear, is called
A. Dedendum
B. Addendum
C. Clearance
D. Working depth
Answer : C

49. In order to double the period of a simple pendulum, the length of the string should be
A. Halved
B. Doubled
C. Quadrupled
D. None of these
Answer : C

50. Angular acceleration of a link can be determined by dividing the
A. Centripetal component of acceleration with length of link
B. Tangential component of acceleration with length of link
C. Resultant acceleration with length of link
D. All of the above
Answer : B