Discuss your findings in a brief report. Also investigate
common methods of wood preservation, and discuss
your findings in your report. What is the environmental
impact of both the production and use of treated wood
products in this question?
17.27. Investigate the common uses of cotton and its typical
properties. Discuss your findings in a brief report.
17.28.As most of you know, commercial transport planes
cruise at an altitude of approximately 10,000 m
(33,000 ft). The power required to maintain
level flight depends on air drag, or resistance, at that
altitude, which may be estimated by the following
relationship:where rairis density of air at the given altitude,CDrep-
resents the drag coefficient of the plane,Ais the plan-
form area, andUrepresents the cruising speed of the
plane. Assume that a plane is moving at constant speed
and,CDremaining constant, determine the ratio of
power that would be required if the plane is cruising
at 8000 m and when the plane may be cruising at
11,000 m.
17.29.Investigate the average daily water consumption per
capita in the United States. Discuss the personal
and public needs in a brief report. Also discuss factorspower
1
2
rairCD AU
3such as geographical location, time of the year, time of
the day, and cost of consumption patterns. For
example, more water is consumed during the early
morning hours. Civil engineers need to consider all
these factors when designing water systems for cities.
Assuming that the life expectancy of people has
increased by five years over the past decades, how much
additional water is needed to sustain the lives of
50 million people?
17.30.When a ring gets stuck on a finger, most people resort
to water and soap as a lubricant to get the ring off. In
earlier times, animal fat was a common lubricant used
in wheel axles. Moving parts in machinery, the piston
inside your car’s engine, and bearings are examples of
mechanical components that require lubrication. A
lubricant is a substance that is introduced between the
parts that have relative motion to reduce wear and fric-
tion. The lubricants must have characteristics that are
suitable for a given situation. For instance, for liquid
lubricants, viscosity is one of the important properties.
The flash and fire, and the cloud and pour points are
examples of other characteristics that are examined
when selecting lubricants. Investigate the use of
petroleum-based lubricants in reducing wear and fric-
tion in today’s mechanical components. Write a brief
report discussing the application and characteristics of
liquid-petroleum-based and solid lubricants that are
commonly used, such as SAE 10W-40 oil and graphite.576 Chapter 17 Engineering Materials
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