ATRACTOR

The applet consists of what we call the display area (with gray background) and menus with buttons, text boxes and value control bars (with blue background). However, it should be noted that, as we will see later, in some cases it is also possible to enter data directly in the visualization area.

Click on the image where you have questions.

Note: The following figures are non-manipulable images. In the figures marked with , if you hover the mouse over them you will see an animation.

The display zone is divided into five areas:

• in the area on the left two pendulums are represented, formed by two balls of mass m and m , suspended by two strings of length L and L, subject to the action of gravity with value g. The pendulum strings rest against a «constraining» surface, which makes the effective pendulum length decrease as the amplitude increases. Drag the balls to the desired starting positions with the mouse;

• in the central area there is a representation of the potential, kinetic and total energies of the pendulum at each instant.

  Dragging the mouse in this area vertically allows you to zoom;

• in the right area (from top to bottom) are representations:
  • the movement of the two pendulums in space (rotate with the mouse to get the best view);
  • of the graphs of the functions x(t) and x(t) in which x(t) and x(t) represent the measurements (in R) of the angles corresponding to the arcs followed by the balls (starting vertically), at time t;
  • of the graphs of the scalar speeds of the balls as a function of time t.

The initial parameters of the pendulums can be modified:

• in the case of the values of the initial angles,
  • directly in the text boxes: and ;
  • dragging the balls;

• in the case of the values of the lengths L and L, the masses m and m of the pendulums and gravity (g),
  • entering the values in the text boxes;

  

  • dragging the control bars.

  

Once these values have been chosen, click on the button , to see the simulation of the movement of the pendulums.

The menu has the following options:

• : to reset the time value (t = 0);
• : to return to the initial configuration.

The option , when selected, makes it possible to have the «constraining surface» for the pendulum strings visible.

In the three areas on the right of the applet, try clicking on them with the right mouse button: you get a menu with other options for manipulating objects.

Among the options, it allows you to have a resizable window of the area where you clicked - for more information, click here.

The flag, at the top of the applet, indicates the language used. If you wish, click on it and select another language:

By clicking , you can choose between:

• : access this instruction page;
• : accesses information about the applet version*.