Answer
Dry road: 25 m/s
Wet road: 12 m/s
Work Step by Step
We know that the necessary centripetal force must equal the force of friction. Thus:
$\frac{mv^2}{r} = \mu_s mg \\ v = \sqrt{\mu_s gr}$
Thus, we find:
a) $v_{max} = \sqrt{\mu_s gr} = \sqrt{.21\times9.81\times73} = 12 \ m/s$
b) $v_{max} = \sqrt{\mu_s gr} = \sqrt{.88\times9.81\times73} = 25 \ m/s$
