A simple pendulum consists of a small ball of mass m=157 g swinging on a massless, inextensible string of length R = 7 m. At time t=0 the pendulum is released from the horizontal position, as shown below. A short time later, the pendulum reaches the bottom of its swing and encounters a nail sticking out of the page a distance L=6.3 m below the pivot point. The pendulum begins to wrap around the nail, and at time t = ttop it is at the top of its first rotation. A. Find acceleration of hall at T =ttop.