Question

A car of mass M is moving on a horizontal circular path of radius r. At an instant its speed is v and is increasing at a rate a.
(a) The acceleration of the car is towards the centre of the path.
(b) The magnitude of the frictional force on the car is greater than $\frac{m{v}^2}{r}$.
(c) The friction coefficient between the ground and the car is not less than a/g.
(d) The friction coefficient between the ground and the car is $\mathrm{\mu }={\tan }^{-1}\frac{v^2}{rg.}$

Answer 1

(b) The magnitude of the frictional force on the car is greater than $\frac{m{v}^2}{r}$.
(c) The friction coefficient between the ground and the car is not less than a/g.

If the magnitude of the frictional force on the car is not greater than $\frac{m{v}^2}{r}$, it will not move forward, as its speed (v) is increasing at a rate a.