✔ 最佳答案
Q: what does natural frequency mean?
Natural frequency of an oscillating system is the frequency demonstrated by the system when it is free to oscillate on its own. It depends on the characteristics of the system. For example, the natural frequency of a simple pendulum only depends on the length of the pendulum suspension.
Q: is that means the pendulums are oscillating with same frequency?
i.e. driving frequency but not natural frequency
The pendulum (i.e. oscillating system) follows more or less the frequency of the driving system.
You may refer to the following web-page which gives a good animation to a forced oscillation system. Try to adjust the driving frequency and observe how the phase difference changes.
http://www.walter-fendt.de/ph14e/resonance.htm
2010-07-18 20:02:23 補充：
Yes, the above answers refer to steady state condition.
