1) Problem Statement: A car travels forward with constant velocity. It goes over a small stone, which gets stuck in the groove of a tire. The initial acceleration of the stone, as it leaves the surface of the road, is (A) vertically upward (B) horizontally forward (C) horizontally backward (D) zero (E) upward and forward, at approximately 45° to the horizontal 2) Relevant Formulas: Objects in a circular path accelerate radially inwards 3) Attempt a) The stone enters a circular path at the wheel's bottom. Thus its centripetal acceleration points upwards b) The stone is accelerated from rest to the car's velocity. Thus, it experiences a translational acceleration rightwards. c) The accelerations are both horizontal and upwards; therefore, e is the right answer The answer key claims that the answer is a.