Why is the normal force of an object sliding down an inclined plane equal to mgcos(θ), whereas for an object moving along a banked road, the normal force of the object is mg/cos(θ)? Also, in some textbooks I see that the frictional force on the object along a banked road is down the inclined plane and contributes to the centripetal force, but in other textbooks I see that the frictional force is in the opposite direction? Great thanks for any clarity! :)