Deck 1: Basic Considerations

Question 1

The mean free path where commercial aircraft fly (about 30,000 ft) is nearest:

A) 0.0076 mm
B) 0.0026 mm
C) 0.00076 mm
D) 0.00016 mm

Answer 1

0.00076 mm

Question 2

If force was selected as a fundamental dimension rather than mass, the units on density would be: (A) $\mathrm { kg } / \mathrm { m } ^ { 3 }$
(B) $\mathrm { N } \cdot \mathrm { s } ^ { 2 } / \mathrm { m } ^ { 4 }$
(C) $\mathrm { N } / \mathrm { s } ^ { 2 } \cdot \mathrm { m } ^ { 2 }$
(D) $\mathrm { s } ^ { 2 } / \mathrm { N } \cdot \mathrm { m } ^ { 2 }$

Answer 2

B
$\mathrm { N } \cdot \mathrm { s } ^ { 2 } / \mathrm { m } ^ { 4 }$
$[ \rho ] = [ \mathrm { m } ] / [ V ] = \left( F \cdot T ^ { 2 } / L \right) / L ^ { 3 } = F \cdot T ^ { 2 } / L ^ { 4 }$ . Using SI units, this is $\underline { \mathrm { N } \cdot \mathrm { s } ^ { 2 } / \mathrm { m } ^ { 4 } }$

Question 3

The fluids that are considered in this text:
(A) Have relatively low viscosities
(B) Must be subjected to a normal stress to have motion
(C) Have molecules that move relatively slowly
(D) Move when subjected to any shear stress

Answer 3

THE FLUIDS THAT ARE CONSIDERED IN THIS TEXT:
(D) Move when subjected to any shear stress
The fluids of interest in Fluid Mechanics always move when subjected to a shearing
stress no matter how small that shearing stress may be.

Question 4

Which of the following is not acceptable in the SI system of units? (A) $\mathrm { N } \cdot \mathrm { cm } / \mathrm { s }$
(B) $\mathrm { kg } / \mathrm { L }$
(C) $\mathrm { m } / \mathrm { ns }$
(D) $\mathrm { J } / \mathrm { m } ^ { 2 }$

Question 5

The energy usage in the United States in 2010 was about 100 × 1018 J. This can be written as:

A) 100 million GJ
B) 1000 million GJ
C) 100 billion MJ
D) 100 trillion MJ