Fluid Mechanics Questions and Answers – Velocity of Sound or Pressure Wave in a Fluid – 1

This set of Fluid Mechanics Multiple Choice Questions & Answers (MCQs) focuses on “Velocity of Sound or Pressure Wave in a Fluid – 1”.

1. Speed is of sound is the _________
a) Distance travelled per unit length
b) Distance travelled per unit time
c) Distance travelled per unit pressure
d) Distance travelled per unit temperature

Explanation: The speed of sound is defined as the distance travelled per unit time. It is due to the sound wave. The sound wave propagates through the medium.

2. The sound wave is transmitted through liquids as_________
a) Longitudinal waves
b) Transverse waves
c) Elongated waves
d) Refracted waves

Explanation: The sound wave is transmitted through liquids, gases and plasma as longitudinal waves. It is also called as compressed waves. Longitudinal waves require a medium to propagate. Thus, the correct answer is Longitudinal waves.

3. What are the assumptions made for a fluid flow through a pipe?
a) Fluid inertia is not taken
b) Viscosity is not taken
c) Volume is not considered
d) Mass is not considered

Explanation: During a fluid flow through a pipe, there are various design considerations. But, the two major assumptions are that the flow is assumed to be fully developed. Also, fluid inertia is not taken into account.

4. Which among the following is not generic property of sound?
a) Viscosity
b) Amplitude
c) Direction
d) Frequency

Explanation: Viscosity is not a generic property sound. It is defined as the property of resistance to flow of fluid. Resistance to flow of fluid takes place when one layer of fluid slides over the other. Viscosity is not a generic property.

5. Sound perceptible by humans has frequencies from _______
a) 20 to 2000 Hz
b) 20 to 20000 Hz
c) 10 to 10000 Hz
d) 30 to 30000 Hz

Explanation: Sounds that are audible to a human ear ranges from 20 to 20000 Hz. At standard temperature and pressure of air, the corresponding wavelengths of sound range from 17m to 17mm.

6. What is the speed of sound in dry air?
a) 331.2 m/s
b) 300 m/s
c) 250 m/s
d) 230 m/s

Explanation: The speed of sound in dry air at a temperature of zero degrees Celsius is equal to 331.2 m/s. Speed of sound in air is denoted by the symbol ‘c’. Thus the correct answer for the following is 331.2 m/s.
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7. What is the speed of sound at 20oC?
a) 331.2 m/s
b) 350 m/s
c) 343 m/s
d) 300 m/s

Explanation: The speed of sound in dry air at a temperature of 20oC is equal to 343 m/s. It is found out using the relation of kilometre and miles. One kilometre = 2.91 seconds, and one mile = 4.69 seconds.

8. Speed of sound in an ideal gas depends on _______
a) Temperature and pressure
b) Surface area and volume
c) Temperature and composition
d) Composition and surface area

Explanation: Speed of sound in ideal gas depends on its composition and temperature. The speed of sound has a weak dependence on frequency and pressure. As there is a slight deviating behaviour in an ideal fluid.

9. Transverse wave is also called as ________
a) Shear wave
b) Compression wave
c) Compressed wave
d) Longitudinal wave

Explanation: Transverse wave is also called as a shear wave. Transverse wave or shear waves occur only in solids. It occurs only in solids because only solids support elastic deformations. It is also called as an elastic wave.

10. Which among the following determines the geometric orientation of transverse waves?
a) Dichroism
b) Optical activity
c) Polarization
d) Photon spin

Explanation: Polarization is defined as a property applied to transverse waves or shear waves. The main function of polarization is to determine the geometric orientation of transverse waves or shear waves.

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