A car is moving along a banked road laid out as a circle of radius r . (a) What should be the banking angle `theta` so that the car travelling at speed v needs no frictional force from tyres to negotiate the turn ? (b) The coefficient of friction between tyres and road are `mu_(s) = 0.9` and `mu_(k) = 0.8` . At what maximum speed can a car enter the curve without sliding toward the top edge of the banked turn ?