Mechanical Vibration MCQ

41. The rate of decay of oscillations is known as

1. logarithmic decrement
2. critical damping
3. damping coefficient
4. transmissibility

42. Critical damping is a function of

1. Mass and stiffness
2. Mass and Damping Coefficient
3. Stiffness and Natural Frequency
4. Natural Frequency and Damping Coefficient

43. The amplitude of underdamping varies with time as

1. Linearly
2. Arithmetically
3. Geometrically
4. Exponentially

44. In forced vibrations the magnitude of damping force at resonance equals

1. inertia force
2. impressed force
3. zero
4. spring force

45. For steady state forced vibrations, phase lag at resonance condition is

1. 0 degree
2. 45 degree
3. 90 degree
4. 180 degree

46. A rotor is said to be rigid if

1. it rotates at rotational speed below 4% of critical speed
2. it rotates at rotational speed below 70% of critical speed
3. it rotates at rotational speed below 60% of critical speed
4. it rotates at rotational speed below 20% of critical speed

47. The type of motion when the acceleration is proportional to displacement is called

1. translation
2. rotational
3. gyroscopic
4. simple harmonic

48. In shafts, critical speed is the speed in which

1. Shafts tends to vibrate violently in  longitudinal direction
2. Shafts tends to vibrate violently in transverse direction
3. Shafts tends to have to and fro motion
4. Shafts rotates on its own axis

49. In a damped vibration system, the damping force is proportional to

1. displacement
2. velocity
3. acceleration
4. applied force

50. Which of the following parameters has higher value during whirling of a shaft?

1. Speed
2. Acceleration
3. Frequency
4. Amplitude