A model known as stopping sight distance is used by civil engineers to design roadways. This simple model estimates the distance a driver needs in order to stop his car while traveling at a certain speed after detecting a hazard. The model proposed by the American Association of State Highway Officials (AASHO) is given by v2 + TV, 2g(f + G) where we have the following. S = stopping sight distance (ft) V = initial speed (ft/s) g = acceleration due to gravity, 32.2 ft/s2 f = coefficient of friction between tires and roadways

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Chapter5: Analysis Of Convection Heat Transfer
Section: Chapter Questions
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A model known as stopping sight distance is used by civil engineers to design roadways. This simple model estimates the
distance a driver needs in order to stop his car while traveling at a certain speed after detecting a hazard. The model proposed
by the American Association of State Highway Officials (AASHO) is given by
v2
S =
2g(f + G)
+ TV,
where we have the following.
S = stopping sight distance (ft)
V = initial speed (ft/s)
g = acceleration due to gravity, 32.2 ft/s2
f = coefficient of friction between tires and roadways
G = grade of road
T = driver reaction time (s)
What are the appropriate units for f and G if the preceding equation is to be homogeneous in units? Show all steps of your
work.
v2
Starting with the equation S
+ TV, the units of S are ft, the units of V2 are --?--
, the units of g are ft/s2,
%3D
2g(f + G)
and the units of the product TV are --?--
Rearranging the equation above to solve for f ± G, we obtain the following.
(Use any variable or symbol stated above as necessary. Do not substitute numerical values; use variables only.)
f+ G =
ft2/s?
Then, the units of f+ G are
= --?--
--?--
Transcribed Image Text:A model known as stopping sight distance is used by civil engineers to design roadways. This simple model estimates the distance a driver needs in order to stop his car while traveling at a certain speed after detecting a hazard. The model proposed by the American Association of State Highway Officials (AASHO) is given by v2 S = 2g(f + G) + TV, where we have the following. S = stopping sight distance (ft) V = initial speed (ft/s) g = acceleration due to gravity, 32.2 ft/s2 f = coefficient of friction between tires and roadways G = grade of road T = driver reaction time (s) What are the appropriate units for f and G if the preceding equation is to be homogeneous in units? Show all steps of your work. v2 Starting with the equation S + TV, the units of S are ft, the units of V2 are --?-- , the units of g are ft/s2, %3D 2g(f + G) and the units of the product TV are --?-- Rearranging the equation above to solve for f ± G, we obtain the following. (Use any variable or symbol stated above as necessary. Do not substitute numerical values; use variables only.) f+ G = ft2/s? Then, the units of f+ G are = --?-- --?--
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