A car is traveling around a banked curve. The angle of the curve is adjusted to be optimum for a velocity of 45 miles/hour. If the car goes around the curve at a speed of 30 miles/hour, which of the following forces will have to exist to allow the car to safely negotiate the curve? a. An additional frictional force up the slope. b. An additional frictional force down the slope. c. An increased normal force on the car. d. The wouldn’t have to be any changes in the forces. If the motion of the car is such as to cause an additional frictional force down the slope of the curve, what would happen to the magnitude of the normal force? a. The normal force would have to decrease. b. The normal force would remain the same. c. The normal force would have to increase.