Question:
If the road of the previous problem is horizontal (no banking), what should be the minimum friction coefficient so that a scooter going at $18 \mathrm{~km} / \mathrm{hr}$. does not skid?
Solution:
Centrifugal force=Frictional force
$\frac{m v^{2}}{R}=\mu \mathrm{N}$
$\frac{m v^{2}}{R}=\mu \mathrm{mg}$
$\mu=\frac{v^{2}}{R g}=\frac{\left(18 \times \frac{5}{48}\right)^{2}}{10 \times 10}$.
$\mu=0.25$