Give the definition simple harmonic motion and write down the defining equation for such motion stating the meaning of any symbols involved.

Simple harmonic motion is defined as a form of periodic motion in which a point or body oscillates in such a way that the acceleration of the point or body is directly proportional to its displacement from the equilibrium position (midpoint) and this acceleration is directed toward the equilibrium position. The defining equation is a = -w²x, where a is the acceleration of the point or body, w its angular frequency (angular displacement per unit time) of the point or body and x is the displacement of the point or body from the equilibrium position. Note the importance of the negative sign in the equation, which shows the acceleration is directed toward the equilibrium position.