About Theory of machines

Following are some of the multiple choice questions on the Theory of machines with answers that will help the students in developing their knowledge.

Theory of machines MCQ

1. The unbalanced primary forces in a reciprocating engine are

  • Balanced by secondary forces
  • Balanced completely
  • Balanced partially
  • Not balanced

2. The partial balancing of reciprocating parts in locomotives produces

  • hammer blow
  • swaying couple
  • variation in tractive force along the line of stroke
  • all of the above

3. When a particle moves round the circumference of a circle of radius r with ω rad/s, then its maximum acceleration is ω2r.

  • Right
  • Wrong

4. Crowning on pulleys helps

  • In increasing velocity ratio
  • In decreasing the slip of the belt
  • For automatic adjustment of belt position so that belt runs centrally
  • Increase belt and pulley life

5. The critical speed of a shaft with a disc supported in between is equal to the natural frequency of the system in

  • Transverse vibrations
  • Torsional vibrations
  • Longitudinal vibrations
  • All of these

6. The equation of motion for a single degree of freedom system with viscous damping is 4(dx²/dt²) + 9(dx/dt) + 16x. The damping ratio of the system is

  • 9/8
  • 9/82
  • 9/16
  • 9/128

7. The example of lower pair is

  • Shaft revolving in a bearing
  • Straight line motion mechanisms
  • Automobile steering gear
  • All of the above

8. The Kutzbach criterion for determining the number of degrees of freedom (n) is (where l = number of links, j = number of joints and h = number of higher pairs)

  • n = 3(l - 1) - 2j - h
  • n = 2(l - 1) - 2j - h
  • n = 3(l - 1) - 3j - h
  • n = 2(l - 1) - 3j - h

9. Which of the following is an example of sliding pair?

  • Piston and cylinder of a reciprocating steam engine
  • Shaft with collars at both ends fitted into a circular hole
  • Lead screw of a lathe with nut
  • Ball and a socket joint

10. The maximum fluctuation of energy is the

  • Difference between the maximum and minimum energies
  • Sum of the maximum and minimum energies
  • Variations of energy above and below the mean resisting torque line
  • Ratio of the mean resisting torque to the work-done per cycle

11. A disturbing mass m₁ attached to the rotating shaft may be balanced by a single mass m₂ attached in the same plane of rotation as that of m₁, such that (where r₁ and r₂ are the radii of rotation of m₁ and m₂ respectively)

  • m₁ r₂ = m₂ r₁
  • m₁ r₁ = m₂ r₂
  • m₁ m₂ = r₁ r₂
  • None of these

12. A chain comprises of 5 links having 5 joints. Is it kinematic chain?

  • Yes
  • No
  • It is a marginal case
  • Data are insufficient to determine it

13. Efficiency of a screw jack is given by

  • tan (α + φ)/tanα
  • tanα/tan (α +φ)
  • tan (α - φ)/tanα
  • tanα/tan (α - φ)

14. A Hartnell governor has its controlling force (Fc) given by Fc = ar + b, where r is the radius of rotation and a and b are constants. The governor becomes isochronous when

  • a is +ve and b = 0
  • a = 0 and b is +ve
  • a is +ve and b is -ve
  • a is +ve and b is also +ve

15. The direction of Coriolis component of acceleration is the direction

  • Of relative velocity vector for the two coincident points rotated by 90° in the direction of the angular velocity of the rotation of the link
  • Along the centripetal acceleration
  • Along tangential acceleration
  • Along perpendicular to angular velocity

16. In a kinematic chain, a quaternary joint is equivalent to

  • One binary joint
  • Two binary joints
  • Three binary joints
  • Four binary joints

17. Which of the following is an open pair?

  • Ball and socket joint
  • Journal bearing
  • Lead screw and nut
  • Cam and follower

18. The motion of a shaft in a circular hole is an example of

  • Completely constrained motion
  • Incompletely constrained motion
  • Successfully constrained motion
  • None of these

19. A universal joint is an example of

  • Higher pair
  • Lower pair
  • Rolling pair
  • Sliding pair

20. 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

  • 1.4 N-s/m
  • 18.52 N-s/m
  • 52.92 N-s/m
  • 529.2 N-s/m

21. The gear train usually employed in clocks is a

  • simple gear train
  • reverted gear train
  • sun and planet gear
  • differential gear

22. In order to give the primary balance of the reciprocating parts of a multi-cylinder in-line engines,

  • the algebraic sum of the primary forces must be equal to zero
  • the algebraic sum of the couples about any point in the plane of the primary forces must be equal to zero
  • both (a) and (b)
  • none of these

23. The frictional torque transmitted in a multi-collared shaft is same as that of a single collared shaft.

  • Right
  • Wrong

24. A circular bar moving in a round hole is an example of

  • Incompletely constrained motion
  • Partially constrained motion
  • Completely constrained motion
  • Successfully constrained motion

25. The D-slide valve is also known as

  • Inside admission valve
  • Outside admission valve
  • Piston slide valve
  • None of these

26. Which of the following is a lower pair?

  • Ball and socket i
  • Piston and cylinder
  • Cam and follower
  • Both (A) and (B) above

27. Critical damping is a function of

  • Mass and stiffness
  • Mass and damping coefficient
  • Mass and natural frequency
  • Damping coefficient and natural frequency

28. The Coriolis component of acceleration is taken into account for

  • Slider crank mechanism
  • Four bar chain mechanism
  • Quick return motion mechanism
  • All of these

29. An automobile steering gear is an example of

  • sliding pair
  • rolling pair
  • lower pair
  • higher pair

30. In a screw jack, the effort required to lower the load W is given by

  • P = W tan(α - φ)
  • P = W tan(α + φ)
  • P = W tan(φ - α)
  • P = W cos(α + φ)

31. In order to balance the reciprocating masses,

  • primary forces and couples must be balanced
  • secondary forces and couples must be balanced
  • both (a) and (b)
  • none of these

32. A pair of friction discs is an example of rolling pair.

  • True
  • False

33. The pressure angle of a cam is the angle between the direction of the follower motion and a normal to the

  • pitch circle
  • base circle
  • pitch curve
  • prime circle

34. If the pressure angle is __________, a reciprocating follower will jam in its bearings.

  • Small
  • Too small
  • Large
  • Too large

35. Governor is used in automobile to

  • Decrease the variation of speed
  • Maximize the fuel economy
  • Limit the vehicle speed
  • Maintain constant engine speed

36. In a Hartnell governor, if a spring of greater stiffness is used, then the governor will be

  • Less sensitive
  • More sensitive
  • Unaffected of sensitivity
  • Isochronous

37. The axis of precession is __________ to the plane in which the axis of spin is going to rotate.

  • Parallel
  • Perpendicular
  • Both A and B
  • None of these

38. The swaying couple is maximum or minimum when the angle of inclination of the crank to the line of stroke (θ) is equal to

  • 90° and 180°
  • 45° and 225°
  • 180° and 270°
  • 270° and 360°

39. A shaft has an attached disc at the centre of its length. The disc has its centre of gravity located at a distance of 2 mm from the axis of the shaft. When the shaft is allowed to vibrate in its natural bow-shaped mode, it has a frequency of vibration of 10 rad/s. When the shaft is rotated at 300 r.p.m., it will whirl with a radius of

  • 2 mm
  • 2.22 mm
  • 2.50 mm
  • 3.0 mm

40. The static friction

  • bears a constant ratio to the normal reaction between the two surfaces
  • is independent of the area of contact, between the two surfaces
  • always acts in a direction, opposite to that in which the body tends to move
  • all of the above

41. The sliding pairs, turning pairs and screw pairs form lower pairs.

  • True
  • False

42. Davis steering gear consists of

  • Sliding pairs
  • Turning pairs
  • Rolling pairs
  • Higher pairs

43. Ackermann steering gear consists of

  • Sliding pairs
  • Turning pairs
  • Rolling pairs
  • Higher pairs

44. Which of the following mechanism is obtained from lower pair?

  • Gyroscope
  • Pantograph
  • Valve and valve gears
  • All of the above

45. A friction circle is a circle drawn when a journal rotates in a bearing. Its radius depends upon the coefficient of friction and the

  • Magnitude of the forces on journal
  • Angular velocity of journal
  • Clearance between journal and bearing
  • Radius of journal

46. A foot step bearing and rotor of a vertical turbine form examples of

  • Incompletely constrained motion
  • Partially constrained motion
  • Completely constrained motion
  • Successfully constrained motion

47. The rotor of a ship rotates in clockwise direction when viewed from stern and the ship takes a right turn. The effect of gyroscopic couple acting on it will be to raise the stern and lower the bow.

  • Agree
  • Disagree

48. Whitworth quick return motion mechanism consists of three turning pairs and one sliding pair.

  • Right
  • Wrong

49. The frequency of damped vibrations with viscous damping is __________ the frequency of undamped vibrations.

  • more than
  • less than
  • same as
  • All of above

50. The gears are termed as medium velocity gears, if their peripheral velocity is

  • 1 - 3 m/s
  • 3 - 15 m/s
  • 15 - 30 m/s
  • 30 - 50 m/s

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