On a curve on a two-lane highway (not divided), a car headed north experiences a centripetal acceleration directed toward the west. Simultaneously, a truck passes the car, headed south, in the other lane. The direction of the centripetal acceleration on the truck is O south north O east O west QUESTION 18 If a ball at the end of a string is whirled in a vertical circle at constant speed, the tension in the string will be O least at the lowest point in the motion O least at a point where the string is parallel to the ground least at the highest point in the motion the same throughout the motion