Problems 245
9.1. Look up the mass of the following objects:
a. recent model of an automobile of your choice
b. the earth
c. a Boeing 777 fully loaded
d. an ant
9.2. The density of standard air is a function of temperature
and may be approximated using the ideal gas law, ac-
cording towhere
rdensity (kg /m
3
)Pstandard atmospheric pressure (101.3 kPa)
Rgas constant; its value for air is 286.9
Tair temperature in Kelvin
Create a table that shows the density of air as a function
of temperature in the range of 0C (273.15 K) to 50C
(323.15 K) in increments of 5C. Also, create a graph
showing the value of density as a function of tempera-
ture.
9.3. Determine the specific gravity of the following materi-
als: gold (r1208 lb/ft
3
), platinum (r1340 lb/ft
3
),
silver (r654 lb/ft
3
), sand (r94.6 lb/ft
3
), freshly
fallen snow (r31 lb/ft
3
), tar (r75 lb/ft
3
), hard
rubber (r74.4 lb/ft
3
).9.4. Show that the specific weight and density are related
according to specific weight (density)(acceleration
due to gravity).
9.5. Compute the values of momentum for the following
situations:
a. a 90-kg football player running at 6 m/s
b. a 1500-kg car moving at a rate of 100 km/h
c. a 200,000-kg Boeing 777 moving at a speed of
500 km/h
d. a bullet with a mass of 15 g traveling at a speed of
500 m/s
e. a 140-g baseball traveling at 120 km/h
f. an 80-kg stunt performer falling off a ten story
building reaching a speed of 30 m/s
9.6. Investigate the mass flow rate of blood through your
heart, and write a brief report to your instructor dis-
cussing your findings.
9.7. Investigate the mass flow rate of oil inside the Alaskan
pipeline, and write a brief report to your instructor dis-
cussing your findings.
9.8. Investigate the mass flow rate of water through the Mis-
sissippi River during a normal year, and write a brief re-
port discussing your findings. Explain flooding using
the conservation of mass statement.
9.9. Determine the mass flow rate of fuel from the gasoline
tank to the car’s fuel injection system. Assume that
the gasoline consumption of the car is 20 mpg when the
car is moving at 60 mph. Use the specific gravity value
of 0.72 for the gasoline.
9.10. Determine the mass moment of inertia for the follow-
ing objects: a thin disk, circular cylinder, and a sphere.a
J
kg#K
b
r
P
RT
- You should have a good understanding of what is meant by mass flow rate and how it is
related to volume flow rate. - You should realize that mass provides a measure of resistance to translational motion. You
should also know that if you want to rotate something, the distribution of mass about the cen-
ter of rotation also plays an important role. The further the mass from a center of rotation,
the more resistance mass offers to rotational motion. - You should know how we define momentum for a moving object. You should also know that
something with a relatively small mass could have a relatively large momentum if it has a
large velocity.
Problems
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