248 Chapter 9 Mass and Mass-Related Parameters
Pipe 1:
d 1 = 1 in.
V 1 = 2 ft/s1 Pipe 2:
d 2 = 1.75 in.
V 2 = 1.5 ft/sPipe 3:
d 3 = 1.5 in.
V 3 =?239.39. Imagine the water level in the tank described in Prob-
lem 9.38 rises at a rate of 0.1 in /s. Knowing the diam-
eter of the tank is 6 in., what is the average velocity of
the water leaving the tank? Express your answer in in /s,
ft /s, and m/s.
9.40. The density of air at a city (such as San Diego) located
at sea level is 1.225 kg /m
3
, while for a city (such as
Denver) located at high altitude is 1.048 kg /m
3. Con-
sider two auditoriums, each with dimensions of 50 ft
100 ft20 ft, one located in San Diego and the
other in Denver. Calculate the mass of air for each au-
ditorium. Express your answer in kg, lbm, and slugs.
9.41. A rectangular duct with dimensions of 12 in.14 in.
delivers conditioned air with a density of 1.2 kg /m
3
to
a room at a rate of 1000 ft
3
/min. What is the mass-
flow rate of air in lbm/h? What is the average air speed
in the duct? Express your answer in m/s and ft /s.
9.42. A rubber balloon has a mass of 10 grams. The balloon
is filled with air and forms a shape that may be ap-
proximated as a sphere with a diameter of 1.5 ft. What
is the total mass of the balloon? What would be the
total mass of the balloon if it is filled with helium in-
stead? Express your answers in grams.
9.43. A typical household of four people consume approxi-
mately 80 gallons of water per day. Express the annual
consumption rate of a city with a population of
100,000 people. Express your answer in slugs per year,
lbmper year, and kg per year.
9.44. Lake Mead, near the Hoover Dam, which is the largest
man-made lake in the United States, contains
28,537,000 acre-foot of water (an acre-foot is the amount
of water required to cover 1 acre to a depth of 1 foot). Ex-
press the mass of the water volume in kg and lbm.
9.45. Air with a density of 0.45 kg /m
3
enters an experimen-
tal jet engine at rate of 180 m/s. The inlet area of the
engine is 5.0 ft
2. After fuel is burned, the air and com-
bustion byproducts leave the engine with a velocity of
650 m/s through an outlet area of 4.0 ft
2
. What is the
average density of the gas exiting the engine? Express
your answer in kg /m
3
, slugs /ft
3
, and lbm/ft
3
.
Air Air + Combustion
Problem 9.38
Problem 9.44
Source:U.S. Bureau of ReclamationProblem 9.45
9.46. In a food processing (drying) application, air (
1.10 kg /m
3
, V10 ft /min) enters a chamber through
a duct with dimensions of 20 in.18 in. and leaves
( 1.25 kg /m
3
) through a ductwork with dimen-
sions of 16 in.18 in. What is the average air speed
in the exit duct? Express your answer in ft /min and m/s.
9.47. To measure the fuel consumption of an experimental
lawn mower, fuel is drawn from a tank that is resting
on a scale, as shown in the figure. The tank and the
fuel have an initial total mass of 10 kg. If the mass scaleCopyright 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