1. The problem statement, all variables and given/known data Assume that there is a hole dug from one side of the earth's surface to another. A ball is dropped through the surface. Explain what happens to acceleration and velocity as the ball passes through the hole. 2. Relevant equations 3. The attempt at a solution I am not sure if I am correct but this what I have attempted. As the ball is moving to the middle, the acceleration should be increasing because the force of gravity is measured from the center and since the distance from the center to the ball is decreasing, acceleration should be increasing and therefore, velocity should also be increasing. At the center, r = 0 which means a = 0. Not sure about velocity ? As the ball is moving away from the center of the earth to the opposite side, a should be decreasing and so velocity should also be decreasing.