Free oscillation occurs when an object, once disturbed, oscillates at its natural frequency without any external force continuously acting upon it. Think of a pendulum swinging after you give it a push, or a guitar string vibrating after you pluck it. The only forces acting are gravity (for the pendulum), tension and elasticity (for the string), and damping forces like air resistance, which gradually reduce the amplitude of the oscillations.
Forced oscillation happens when an external periodic force is applied to an oscillating system, causing it to oscillate at the frequency of the applied force. Imagine pushing a child on a swing repeatedly, or the vibrations of a washing machine when the motor is running. The system is 'forced' to oscillate, and its frequency is dictated by the external driving force, not its natural frequency.
| Feature | Free Oscillation | Forced Oscillation |
|---|---|---|
| Definition | Oscillation at natural frequency after initial disturbance. | Oscillation driven by an external periodic force. |
| Frequency | Natural frequency of the system. | Frequency of the external driving force. |
| External Force | No continuous external force. | Continuous external periodic force. |
| Amplitude | Decreases over time due to damping. | Maintained by the external force; depends on driving frequency and damping. |
| Examples | Pendulum swinging, guitar string vibrating. | Swing being pushed, washing machine vibrating, speaker cone vibrating. |
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