DOM MCQ-IV

When there is a reduction in amplitude over every cycle of vibration, then the body is said to have

• a) free vibration

• b) forced vibration

• c) damped vibration

• d) none of the mentioned

Longitudinal 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 the mentioned

The factor which affects the critical speed of a shaft is

• a) diameter of the disc

• b) span of the shaft

• c) eccentricity

• d) all of the mentioned

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

In vibration isolation system, if ω/ωn is less than √2 , then for all values of the damping factor, the transmissibility will be

where ω = Circular frequency of the system in rad/s, and

ωn = Natural circular frequency of vibration of the system in rad/s.

• a) less than unity

• b) equal to unity

• c) greater than unity

• d) zero

In vibration isolation system, if ω/ωn > 1, then the phase difference between the transmitted force and the disturbing force is

• a) 0°

• b) 90°

• c) 180°

• d) 270°

If the spring displacement is high then the frequency of the spring increases.

• a) True

• b) False

Static deflection and frequency are independent of each other.

• a) True

• b) False

For the same dimensions of a beam, transverse vibrations have a lower frequency than longitudinal frequency.

• a) True

• b) False

For the same dimensions of the shaft which of the following has the greater natural frequency?

• a) Transverse

• b) Longitudinal

• c) Depends on thickness

• d) Depends upon length