I ended up finding a solution for this question, but I am not understanding the last part of it. How did they simply the part outlined in red to ft/ft? I may be overthinking this, but I can't seem to figure it out.
I ended up finding a solution for this question, but I am not understanding the last part of it. How did they simply the part outlined in red to ft/ft? I may be overthinking this, but I can't seem to figure it out.
College Physics
11th Edition
ISBN:9781305952300
Author:Raymond A. Serway, Chris Vuille
Publisher:Raymond A. Serway, Chris Vuille
Chapter1: Units, Trigonometry. And Vectors
Section: Chapter Questions
Problem 1CQ: Estimate the order of magnitude of the length, in meters, of each of the following; (a) a mouse, (b)...
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I ended up finding a solution for this question, but I am not understanding the last part of it. How did they simply the part outlined in red to ft/ft? I may be overthinking this, but I can't seem to figure it out.

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
= --?--
--?--

Transcribed Image Text:Formula used:
The model proposed by the American Association of State Highway
Officials (AASHO) is,
v?
+ TV (1)
2g(f±G)
S =
Here,
S is the stopping sight distance,
V is the initial speed,
f is the coefficient of friction between tires and roadways,
G is grade of road,
g is the acceleration due to gravity, and
T is the driver reaction time.
Calculation:
Rearrange the equation (1)
as follows,
y2
2g(f±G)
(2)
S- TV =
V2
(f ± G) =
2g(S–TV)
Substitute the unit ft for S, " for V, s for T and " for g in equation
(2) to find f and G.
(#)'
2(골) (1-10)())
(2)
2(플)(R-10)
(f± G) =
The ratio of " is results to G, f are unitless.
Therefore, the grad of road (G) and coefficient of friction (f) are
unitless.
Conclusion:
Hence, the grad of road (G) and coefficient of friction (f) are
unitless.
Expert Solution
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