Which component provides the centripetal force for a vehicle moving at an optimum speed on a banked road?

$A$ lorry is moving on a smooth circular path of radius $50 \ m$ with a velocity of $20 \ ms^{-1}$. Then the banking angle of the road is (Acceleration due to gravity $= 10 \ ms^{-2}$)

What is the angle of banking of a railway track of radius of curvature $250 \,m$, if the maximum velocity of the train is $90 \,km/h$? $(g=10 \,ms^{-2})$

The radius of a curved road on a national highway is $R$. The width of the road is $b$. The outer edge of the road is raised by $h$ with respect to the inner edge so that a car with velocity $v$ can pass safely over it. The value of $h$ is

Define optimum speed.

On a railway curve,the outside rail is laid higher than the inside one so that the resultant force exerted on the wheels of the rail car by the tops of the rails will: