Curves in the road are banked with the outside of the curve higher than the inside of the curve. Banking allows a care to make the curve at a higher speed. Why?

Question

a. The bank reduces the amount of centripetal force needed to make the turn

b. The friction coefficient increases when the road is banked

c. The bank allows a component of the normal force to contribute to the centripetal force

d. Curves aren't really banked; your teacher is making this stuff up

Answer 1

The answer is (c). The bank doesn't change the centripetal force which depends on speed and radius of the turn. The coefficient of friction only depends on the materials in contact with each other, here the tires and the pavement. But when the surface is tilted from horizontal, the normal (= perpendicular to surface) force now has a horizontal component in the same direction as the centripetal force.