Vibrations, whose amplitudes of oscillations decrease with time, are called

Options

A. free vibrations
B. forced vibrations
C. damped vibrations
D. none of these

Explanation

To solve the question regarding vibrations whose amplitudes of oscillations decrease with time, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Vibration Types**:
- We need to identify the types of vibrations mentioned in the options: Free Vibration, Forced Vibration, and Damped Vibration.

2. **Free Vibration**:
- Free vibration occurs when a system oscillates without any external force acting on it. The system vibrates at its natural frequency, and the amplitude does not necessarily decrease over time unless there are other factors involved.

3. **Forced Vibration**:
- Forced vibration happens when an external force is applied to the system. The system is driven by this external force, and while it may oscillate, the amplitude does not inherently decrease over time due to the presence of the external force.

4. **Damped Vibration**:
- Damped vibration is characterized by a gradual reduction in the amplitude of oscillations over time. This occurs because energy is lost from the system, often due to friction or resistance. As energy is dissipated, the amplitude of the oscillations decreases.

5. **Conclusion**:
- Since the question specifically asks for vibrations whose amplitudes decrease with time, the correct answer is **Damped Vibration**.

### Final Answer:
The vibrations whose amplitudes of oscillations decrease with time are called **Damped Vibration** (Option 3).

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