Question

A curved road is banked for speed $v_{0}$. When a car moves along the road with a constant speed $v$, the force of friction between the road and the tyres is $F$. Which of the following statements(s) is (are) correct?
(1) If $v=v_{0}, F=0$
(2) If $v < v_{0}, F$ acts outwards
(3) If $v > v_{0}, F$ acts inwards
(4) If $v=0, F=0$

• A. 1, 2 and 3 are correct
• B. 1 and 2 are correct
• C. 2 and 4 are correct
• D. 1 and 3 are correct

Answer 1

Answer: (A)

When $v=v_{0}$, banking of road is capable in itself in providing the necessary centripetal force.
So, the force of friction $F=0$.
When $v=0, F$ is outwards, for the equilibrium of car $(F=m g \sin \theta)$
When $v < v_{0}, F$ is again outwards.
when $v > v_{0}$, banking in itself is not capable for providing the necessary centripetal force.
So, the force of friction $F$ acts inwards.