Explain the forces involved in a pendulum set up.

Just as the pendulum is released, the pendulum ball is at its maximum acceleration. The force due to gravity (weight) is acting vertically downwards, giving it a force component acting perpendicular to the string. This causes the acceleration. There is also tension in the string that opposes the component of the weight parallel to the string. In the stage of equilibrium, when the string is vertical, the forces of tension in the string and weight of the ball act in the same plane and cancel each other out. Hence there is no acceleration. There is no force component acting in the horizontal direction.At the second peak of the pendulum, the forces acting are the same as when the pendulum is first released, only acting in the opposite direction.