## Question 7: Explain what is damped oscillation.

### Damped oscillation or damped harmonic oscillation

When the amplitude of oscillation steadily decreases with time, the oscillation is said to be damped oscillation.

Explanation:  When an oscillator, like a pendulum, is set into vibration and there is no force acting on it then the pendulum keeps on vibrating with constant amplitude and time period. However, this is an ideal situation. In practice, it is quite rare to see a pendulum oscillating with constant amplitude forever. This is because there is always some force resisting the motion of the oscillator. For example, in case of simple pendulum air resists the motion of the bob. As a result, the pendulum or any oscillator, do work against this resistive force. Therefore, its energy continuously decreases in overcoming this resistance. As the energy of the pendulum decreases, its amplitude also decreases the same way. Finally, the amplitude becomes zero and all the energy of the oscillator is dissipated in the resistive surroundings. Such an oscillation is called damped oscillation (or damped harmonic oscillation).

(A) An oscillation is damped due to
1. Mechanical force
2. Restoring force
3. Frictional force
(B) Shock absorbers in automobiles is one practical example of
1. Linear oscillations
2. Damped oscillations
3. Random oscillations
(3) In damped oscillations, the amplitude change with time as,
1. Exponentially
2. Linearly
3. Randomly

Remember these points about damped oscillation

1. When the amplitude of the oscillating body continuously decreasing and finally comes to its mean position (zero amplitude) the oscillation is said to be a damped oscillation.
2. There is a dissipating force that resists the motion of the oscillator.
3. The resistive force opposes the motion of the oscillator and for greater velocity of the oscillator, the resistance force is also large and vice versa.
4. The decrease in the amplitude with time is exponential.