The vibrating body which shows the vibrations as shown in the diagram is tuning fork vibrating in the air. Here, during its vibration, it has to resist the air friction which is offered by the air particles. As a result tuning fork loses its energy resulting in the decrease of the amplitude of its vibration. Such vibrations are called damped vibrations. Damped vibrations are the periodic vibrations of decreasing amplitude in the presence of resistive force. The amplitude of motion decreases due to the friction (or resistive) force which the surrounding medium exerts on the body vibrating it. Due to this resistive force, the vibrating body continuously loses its energy in doing work against the force of friction and so its amplitude gradually decreases.