# Steam and Gas Turbines Questions and Answers – Elementary Gas Dynamics

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This set of Steam and Gas Turbines Multiple Choice Questions & Answers (MCQs) focuses on “Elementary Gas Dynamics”.

1. Continuous flow of fluid is called as _______
a) Continuum
b) Invincible flow
c) Continuum & Invincible flow
d) None of the mentioned

Explanation: Continuous flow of fluid is called continuum.

2. Knudsen number does not have any __________
a) units & dimension
b) units
c) dimension
d) none of the mentioned

Explanation: Knudsen number does not have any dimension and units.

3. Continuum in fluids is predicted by using ________
a) Knudsen number
b) Mach number
c) Knudsen & Mach number
d) None of the mentioned

Explanation: Continuum in fluids is predicted by using Knudsen number. Mach number is used to define the speed of sound proportionality.

4. Ratio of mean free path to characteristic length is called as _________
a) Mach number
b) Knudsen number
c) Nusselt number
d) None of the mentioned

Explanation: Ratio of mean free path to characteristic length is called Knudsen number. Nusselt number is used in heat transfer.

5. Distance traveled by the molecule in between successive collisions is called as __________
a) mean free path
b) kinetic path
c) mean free path & kinetic path
d) none of the mentioned

Explanation: Distance traveled by the molecule in between successive collisions is called as mean free path.

6. Knudsen number is less than _______
a) 1
b) 0.5
c) 0.3
d) none of the mentioned

Explanation: Knudsen number is in between 0 and 0.3.

7. Continuum equations are valid only when Knudsen number is ________ than 0.3.
a) greater
b) less
c) equal
d) none of the mentioned

Explanation: Continuum equations are valid only when Knudsen number is less than 0.3

8. When altitude of earth is in between 90 km and 150 km Knudsen number can be in between 0.3 and _________
a) 1
b) 2
c) 3
d) 4

Explanation: When altitude of earth is in between 90 km and 150 km Knudsen number can be in between 0.3 and 1.

9. Knudsen number ranges in between 0.3 and 1 in ________
a) boundary & transient region
b) boundary region
c) transient region
d) none of the mentioned

Explanation: Knudsen number ranges in between 0.3 and 1 in transient region.

10. Kinetic theory of gasses are applicable only when Knudsen number is greater than 1.
a) True
b) False 