Question

A vehicle is moving without slipping or skidding on a circular road, which is rough and banked. Then choose the correct option for the possible direction of friction

• A. Up the incline
• B. Down the incline
• C. Both (a) and (b)
• D. None of the above

Answer 1

The correct option is C Both (a) and (b)

The direction of friction will be dictated by direction of slipping of vehicle, since friction will act in a direction to oppose the slipping.

We know the equation for circular motion:
$F_{centripetal}=\frac{m{v}^2}{r}$

If speed of vehicle( $v$) is very high, vehicle will tend to slip outwards. Since, to sustain a large speed, vehicle needs to move on a larger radius. So the frictional force will act down the incline to stop slipping.

However, if speed of vehicle( $v$) is on lower side, vehicle tends to slip down the incline. Hence, frictional force will be acting up the plane, to prevent slipping.

$\therefore$ option (c) is correct.