Question

Two friends are driving in a car, going around a turn at a constant speed. Leslie says that a force is required to make the turn, but Caroline says that no force is required, because they are traveling at a constant speed, which friend is correct, and why?

Answer 1

Leslie is correct. The car may be turning with a constant speed, but it is constantly accelerating toward the center of the circle made by the turn in order to maintain a constant tangential speed. Acceleration means force - an object that is accelerating or slowing down is feeling the effect of some external force. This force is provided by static friction between the tires and the road.