There are three springs all driven by external force with different frequency.
The resonance frequency is determined by $\omega_0=\sqrt{k/m}$ where k is the spring constant, m is the mass (k,m can be adjusted with slider).
When sync check box is checked:
The driven frequency for left spring is $ratio*w_0$,
The driven frequency for center spring is $w_0$,
The driven frequency for right spring is $ratio/w_0$.

You can find the phase between oscillation and external force.
A damping force is introduced to prevent the amplitude become infinity.

/htdocs/ntnujava/ejsuser/2/users/ntnu/fkh/drivenpendulum_pkg/drivenpendulum.propertiesFull screen applet or Problem viewing java?Add http://www.phy.ntnu.edu.tw/ to exception site list