An idealized model of a point mass suspended from a non-elastic and massless string is known as a simple pendulum. Consider a top, freely suspended from a string fixed to a pivot point. It experiences a gravitational force and tension in the string. At the equilibrium position, both these forces balance each other. When the top is displaced by a small angular displacement and released, it starts oscillating back and forth, executing simple harmonic motion. The gravitational force at the displaced position is resolved into radial and tangential forces. The radial component counters the tension in the string. The restoring torque acting into the plane equals the tangential component times the string length and brings the top back to the equilibrium position. In a simple pendulum, the restoring force is directly proportional to the displacement along the arc. By modifying the equations of simple harmonic motion, the period of a simple pendulum is obtained.