Course Contents > ... > Ch. 3: Vectors and Motion in 2D > Throwing a Stone Throwing a Stone You are throwing a stone up into the air. Neglecting friction, when it is in the air :.. the acceleration is directly proportional to the velocity, the vertical component of the velocity changes sign at the top of the motion. the acceleration is "up" while it is still moving up, and "down" when it is on the way down the acceleration is zero at the top point of the motion. the vertical component of the velocity is constant. O acceleration and velocity always point in opposite directions. Submit Answer Incorrect. Tries 1/4 Previous Tries Post Discussion