The motion in which the position of a body repeats after the fixed interval of time is known as periodic or harmonic motion. A harmonic motion is simplest type i.e. constant amplitude and simple frequency is known as simple harmonic motion. A body moves to and fro about it’s mean position, the acceleration so produced is directly proportional to the displacement 9y0 and is always directed towards the mean position.
This note provides an information about simple pendulum ,time period , the vibration of a particle in a horizontal spring .where ω2=kmω2=km is a constant. This shows that the acceleration is directly proportional to the displacement and is directed towards the ean position. Hence, the motion of a horizontal mass-spring system is simple harmonic motion.
If a body is set in vibration by an external periodic force whose frequency is equal to the natural frequency of the vibrating body, the amplitude of vibration increases at each step and becomes very large. Such vibration is called resonant vibration. When a system oscillating is given some initial displacement from its equilibrium position and left free, it begins to oscillate with its own frequency with constant amplitude. Then the oscillation of the body is called free oscillation.