Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

274 Chapter 10 Force and Force-Related Parameters

Example 10.9 Starting with an atmospheric pressure of 101,325 Pa, express the magnitude of the pressure

in the following units: (a) millimeters of mercury ( mmHg), (b) inches of mercury (inHg),

(c) meters of water, and (d) feet of water. The densities of water and mercury are 

1,000 kg /m

3

and rHg13,550 kg /m

3

respectively.

(a) We start with the relationship between the height of a fluid column and the pressure

at the base of the column, which is

And solving forh, we have

Therefore, the pressure due to a standard atmosphere is equal to the pressure created at a base

of a 760-mm-tall column of mercury. Stated another way, 1 atm 760 mmHg.

h0.76 m760 mm

Prgh101,325a

N

m

2 b13,550a

kg

m

3 bc9.81a

m

s

2 bdh^1 m^2

rH

2 O

TABLE 10.4 Variation of Standard Atmosphere

with Altitude

Atmospheric Air Density

Altitude (m) Pressure (kPa) (kg /m

3

)

0 (sea level) 101.325 1.225

500 95.46 1.167

1000 89.87 1.112

1500 84.55 1.058

2000 79.50 1.006

2500 74.70 0.957

3000 70.11 0.909

3500 65.87 0.863

4000 61.66 0.819

4500 57.75 0.777

5000 54.05 0.736

6000 47.22 0.660

7000 41.11 0.590

8000 35.66 0.526

9000 30.80 0.467

10,000 26.50 0.413

11,000 22.70 0.365

12,000 19.40 0.312

13,000 16.58 0.266

14,000 14.17 0.228

15,000 12.11 0.195

Source:Data from U.S. Standard Atmosphere (1962).

62080_10_ch10_p251-302.qxd 5/22/10 12:32 AM Page 274

Copyright 2010 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).

圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀圀圀圀⸀夀䄀娀䐀䄀一倀刀䔀匀匀⸀䌀伀䴀