Forced vibration is a type of vibration that occurs when a system is subjected to an external force or excitation, causing it to vibrate at a specific frequency. This external force can be periodic or non-periodic, and the system may or may not have its natural frequency of vibration in sync with the external force.
Free vibration occurs when a system is allowed to vibrate without any external force acting upon it. In contrast, forced vibration is caused by an external force acting on the system. This external force can significantly affect the amplitude and frequency of the vibration, unlike free vibration where the amplitude and frequency are solely determined by the system's natural characteristics.
The main difference between forced vibration and combined SHM (simple harmonic motion) is that forced vibration is always caused by an external force, while combined SHM is a type of vibration that can occur naturally in a system with multiple degrees of freedom. Combined SHM is a combination of two or more simple harmonic motions with different frequencies and amplitudes.
No, combined SHM cannot be considered as a type of forced vibration because it occurs naturally in a system with multiple degrees of freedom, without any external force acting on it. In combined SHM, the oscillations are caused by the system's own natural frequencies and not by an external force.
Forced vibration can be observed in various scenarios, such as when a car is running on a bumpy road, causing the vehicle to vibrate due to the external force of the road's irregularities. On the other hand, combined SHM can be seen in objects like a pendulum, with the combination of its oscillations in different directions creating a combined SHM motion. Another example is a swinging bridge, where the combination of its vertical and horizontal oscillations forms a combined SHM pattern.