# Thermodynamics Questions and Answers – Velocity of Pressure Pulse in a Fluid and Stagnation Properties

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This set of Thermodynamics Multiple Choice Questions & Answers (MCQs) focuses on “Velocity of Pressure Pulse in a Fluid and Stagnation Properties”.

1. An incompressible fluid is one for which density does not change with change in ____
a) pressure
b) temperature
c) velocity
d) all of the mentioned

Explanation: In an incompressible fluid, either density does not change or changes very little.

2. A compressible fluid is one for which density changes with change in temperature, pressure or velocity.
a) true
b) false

Explanation: This is opposite to an incompressible fluid.

3. Liquids are ____ and gases are ____
a) both are compressible
b) both are incompressible
c) incompressible, compressible
d) compressible, incompressible

Explanation: Liquids are incompressible whereas gases are compressible.

4. The pressure wave velocity c is given by
a) 1 / (dp/d(density))
b) sqrt(dp/d(density))
c) sqrt(d(density)/dp)
d) (dp/d(density))

Explanation: Here dp is the change in pressure.

5. For an ideal gas, velocity of sound is given by
a) 1/ɣ*R*T
b) sqrt(1/ɣ*R*T)
c) sqrt(ɣ/RT)
d) sqrt(ɣ*R*T)

Explanation: Here R is the characteristic gas constant.

6. The lower the molecular weight of fluid, ____ the value of ɣ and ____ is the sonic velocity at same temperature.
a) lower, lower
b) higher, higher
c) lower, higher
d) higher. lower

Explanation: This comes from the expression of velocity of sound in an ideal gas.

7. The Mach number is given by
a) (c/V)2
b) (V/c)2
c) V/c
d) c/V

Explanation: Here V is the actual velocity and c is the sonic velocity.

8. For the isentropic stagnation state,
a) it is a reference state
b) designated with subscript zero
c) both of the mentioned
d) none of the mentioned

Explanation: It is a reference state in compressible fluid flow.

9. The reference temperature To and normal temperature T are related by
a) (To/T) = 1 + (V2)/(2*cp*T)
b) (To/T) = 1 – (V2)/(2*cp*T)
c) (To/T) = 1 + (V2)/(cp*T)
d) (To/T) = 1 – (V2)/(cp*T)

Explanation: Here cp is the specific heat at constant pressure and V is the actual velocity.

10. The reference temperature To and normal temperature T can be related in terms of M by
a) (To/T) = 1 + (ɣ-1)*(M2)
b) (To/T) = 1 + (ɣ-1)*(M2)/2
c) (To/T) = 1 – (ɣ-1)*(M2)/2
d) (To/T) = 1 – (ɣ-1)*(M2)  