
272 Forensic Engineering Fundamentals
in their calculations. For example, when μ = 0.8 with one wheel skidding, they will adjust
the coecient by dividing by four so that they use μ = 0.2. In other instances, when two
skid marks are deposited, one longer than the other, they will average the length of the skid
marks and use this value as the skid distance. In both cases they are aecting the equation
used to calculate the minimum speed from skid marks, namely,
D
s
= 2 µ
(9.127)
where
v
s
is the minimum speed (/s)
g is the acceleration due to gravity (32.2 /s
2
)
μ is the coecient of friction or “drag coecient”
D is the skid distance ()
e number ...